diff --git a/ErsatzTV.Application/MediaCollections/Commands/PreviewPlaylistPlayoutHandler.cs b/ErsatzTV.Application/MediaCollections/Commands/PreviewPlaylistPlayoutHandler.cs
index 097717038..c9905a494 100644
--- a/ErsatzTV.Application/MediaCollections/Commands/PreviewPlaylistPlayoutHandler.cs
+++ b/ErsatzTV.Application/MediaCollections/Commands/PreviewPlaylistPlayoutHandler.cs
@@ -1,5 +1,6 @@
 using System.Diagnostics.CodeAnalysis;
 using ErsatzTV.Application.Scheduling;
+using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Domain.Scheduling;
 using ErsatzTV.Core.Interfaces.Repositories;
@@ -57,65 +58,70 @@ public class PreviewPlaylistPlayoutHandler(
         // TODO: make an explicit method to preview, this is ugly
         playoutBuilder.TrimStart = false;
         playoutBuilder.DebugPlaylist = playout.ProgramSchedule.Items[0].Playlist;
-        PlayoutBuildResult result = await playoutBuilder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await playoutBuilder.Build(
             DateTimeOffset.Now,
             playout,
             referenceData,
             PlayoutBuildMode.Reset,
             cancellationToken);
 
-        var maxItems = 0;
-        Dictionary<PlaylistItem, List<MediaItem>> map =
-            await mediaCollectionRepository.GetPlaylistItemMap(
-                playout.ProgramSchedule.Items[0].Playlist,
-                cancellationToken);
-        foreach (PlaylistItem item in playout.ProgramSchedule.Items[0].Playlist.Items)
-        {
-            if (item.PlayAll)
-            {
-                maxItems += map[item].Count;
-            }
-            else
+        return await buildResult.MatchAsync(
+            async result =>
             {
-                maxItems += 1;
-            }
-        }
+                var maxItems = 0;
+                Dictionary<PlaylistItem, List<MediaItem>> map =
+                    await mediaCollectionRepository.GetPlaylistItemMap(
+                        playout.ProgramSchedule.Items[0].Playlist,
+                        cancellationToken);
+                foreach (PlaylistItem item in playout.ProgramSchedule.Items[0].Playlist.Items)
+                {
+                    if (item.PlayAll)
+                    {
+                        maxItems += map[item].Count;
+                    }
+                    else
+                    {
+                        maxItems += 1;
+                    }
+                }
 
-        // limit preview to once through the playlist
-        var onceThrough = result.AddedItems.Take(maxItems).ToList();
+                // limit preview to once through the playlist
+                var onceThrough = result.AddedItems.Take(maxItems).ToList();
 
-        // load playout item details for title
-        foreach (PlayoutItem playoutItem in onceThrough)
-        {
-            Option<MediaItem> maybeMediaItem = await dbContext.MediaItems
-                .AsNoTracking()
-                .Include(mi => (mi as Movie).MovieMetadata)
-                .Include(mi => (mi as Movie).MediaVersions)
-                .Include(mi => (mi as MusicVideo).MusicVideoMetadata)
-                .Include(mi => (mi as MusicVideo).MediaVersions)
-                .Include(mi => (mi as MusicVideo).Artist)
-                .ThenInclude(mm => mm.ArtistMetadata)
-                .Include(mi => (mi as Episode).EpisodeMetadata)
-                .Include(mi => (mi as Episode).MediaVersions)
-                .Include(mi => (mi as Episode).Season)
-                .ThenInclude(s => s.SeasonMetadata)
-                .Include(mi => (mi as Episode).Season.Show)
-                .ThenInclude(s => s.ShowMetadata)
-                .Include(mi => (mi as OtherVideo).OtherVideoMetadata)
-                .Include(mi => (mi as OtherVideo).MediaVersions)
-                .Include(mi => (mi as Song).SongMetadata)
-                .Include(mi => (mi as Song).MediaVersions)
-                .Include(mi => (mi as Image).ImageMetadata)
-                .Include(mi => (mi as Image).MediaVersions)
-                .SelectOneAsync(mi => mi.Id, mi => mi.Id == playoutItem.MediaItemId, cancellationToken);
+                // load playout item details for title
+                foreach (PlayoutItem playoutItem in onceThrough)
+                {
+                    Option<MediaItem> maybeMediaItem = await dbContext.MediaItems
+                        .AsNoTracking()
+                        .Include(mi => (mi as Movie).MovieMetadata)
+                        .Include(mi => (mi as Movie).MediaVersions)
+                        .Include(mi => (mi as MusicVideo).MusicVideoMetadata)
+                        .Include(mi => (mi as MusicVideo).MediaVersions)
+                        .Include(mi => (mi as MusicVideo).Artist)
+                        .ThenInclude(mm => mm.ArtistMetadata)
+                        .Include(mi => (mi as Episode).EpisodeMetadata)
+                        .Include(mi => (mi as Episode).MediaVersions)
+                        .Include(mi => (mi as Episode).Season)
+                        .ThenInclude(s => s.SeasonMetadata)
+                        .Include(mi => (mi as Episode).Season.Show)
+                        .ThenInclude(s => s.ShowMetadata)
+                        .Include(mi => (mi as OtherVideo).OtherVideoMetadata)
+                        .Include(mi => (mi as OtherVideo).MediaVersions)
+                        .Include(mi => (mi as Song).SongMetadata)
+                        .Include(mi => (mi as Song).MediaVersions)
+                        .Include(mi => (mi as Image).ImageMetadata)
+                        .Include(mi => (mi as Image).MediaVersions)
+                        .SelectOneAsync(mi => mi.Id, mi => mi.Id == playoutItem.MediaItemId, cancellationToken);
 
-            foreach (MediaItem mediaItem in maybeMediaItem)
-            {
-                playoutItem.MediaItem = mediaItem;
-            }
-        }
+                    foreach (MediaItem mediaItem in maybeMediaItem)
+                    {
+                        playoutItem.MediaItem = mediaItem;
+                    }
+                }
 
-        return onceThrough.OrderBy(i => i.StartOffset).Map(Scheduling.Mapper.ProjectToViewModel).ToList();
+                return onceThrough.OrderBy(i => i.StartOffset).Map(Scheduling.Mapper.ProjectToViewModel).ToList();
+            },
+            _ => []);
     }
 
     private static ProgramScheduleItemFlood MapToScheduleItem(PreviewPlaylistPlayout request) =>
diff --git a/ErsatzTV.Application/Playouts/Commands/BuildPlayoutHandler.cs b/ErsatzTV.Application/Playouts/Commands/BuildPlayoutHandler.cs
index aa968392f..64b86f062 100644
--- a/ErsatzTV.Application/Playouts/Commands/BuildPlayoutHandler.cs
+++ b/ErsatzTV.Application/Playouts/Commands/BuildPlayoutHandler.cs
@@ -124,26 +124,31 @@ public class BuildPlayoutHandler : IRequestHandler<BuildPlayout, Either<BaseErro
                 playout.ScheduleKind);
             string channelNumber = referenceData.Channel.Number;
             channelName = referenceData.Channel.Name;
-            PlayoutBuildResult result = PlayoutBuildResult.Empty;
+            Either<BaseError, PlayoutBuildResult> buildResult = BaseError.New("Unsupported schedule kind");
 
             switch (playout.ScheduleKind)
             {
                 case PlayoutScheduleKind.Block:
-                    result = await _blockPlayoutBuilder.Build(
+                    buildResult = await _blockPlayoutBuilder.Build(
                         request.Start,
                         playout,
                         referenceData,
                         request.Mode,
                         cancellationToken);
-                    result = await _blockPlayoutFillerBuilder.Build(
-                        playout,
-                        referenceData,
-                        result,
-                        request.Mode,
-                        cancellationToken);
+
+                    foreach (var result in buildResult.RightToSeq())
+                    {
+                        buildResult = await _blockPlayoutFillerBuilder.Build(
+                            playout,
+                            referenceData,
+                            result,
+                            request.Mode,
+                            cancellationToken);
+                    }
+
                     break;
                 case PlayoutScheduleKind.Sequential:
-                    result = await _sequentialPlayoutBuilder.Build(
+                    buildResult = await _sequentialPlayoutBuilder.Build(
                         request.Start,
                         playout,
                         referenceData,
@@ -151,7 +156,7 @@ public class BuildPlayoutHandler : IRequestHandler<BuildPlayout, Either<BaseErro
                         cancellationToken);
                     break;
                 case PlayoutScheduleKind.Scripted:
-                    result = await _scriptedPlayoutBuilder.Build(
+                    buildResult = await _scriptedPlayoutBuilder.Build(
                         request.Start,
                         playout,
                         referenceData,
@@ -164,7 +169,7 @@ public class BuildPlayoutHandler : IRequestHandler<BuildPlayout, Either<BaseErro
                 case PlayoutScheduleKind.None:
                 case PlayoutScheduleKind.Classic:
                 default:
-                    result = await _playoutBuilder.Build(
+                    buildResult = await _playoutBuilder.Build(
                         request.Start,
                         playout,
                         referenceData,
@@ -173,123 +178,134 @@ public class BuildPlayoutHandler : IRequestHandler<BuildPlayout, Either<BaseErro
                     break;
             }
 
-            var changeCount = 0;
+            return await buildResult.MatchAsync<Either<BaseError, PlayoutBuildResult>>(
+                async result =>
+                {
+                    var changeCount = 0;
 
-            if (result.RerunHistoryToRemove.Count > 0)
-            {
-                changeCount += await dbContext.RerunHistory
-                    .Where(rh => result.RerunHistoryToRemove.Contains(rh.Id))
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    if (result.RerunHistoryToRemove.Count > 0)
+                    {
+                        changeCount += await dbContext.RerunHistory
+                            .Where(rh => result.RerunHistoryToRemove.Contains(rh.Id))
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            if (result.AddedRerunHistory.Count > 0)
-            {
-                changeCount += 1;
-                await dbContext.BulkInsertAsync(result.AddedRerunHistory, cancellationToken: cancellationToken);
-            }
+                    if (result.AddedRerunHistory.Count > 0)
+                    {
+                        changeCount += 1;
+                        await dbContext.BulkInsertAsync(result.AddedRerunHistory, cancellationToken: cancellationToken);
+                    }
 
-            if (result.ClearItems)
-            {
-                changeCount += await dbContext.PlayoutItems
-                    .Where(pi => pi.PlayoutId == playout.Id)
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    if (result.ClearItems)
+                    {
+                        changeCount += await dbContext.PlayoutItems
+                            .Where(pi => pi.PlayoutId == playout.Id)
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            foreach (DateTimeOffset removeBefore in result.RemoveBefore)
-            {
-                changeCount += await dbContext.PlayoutItems
-                    .Where(pi => pi.PlayoutId == playout.Id)
-                    .Where(pi => pi.Finish < removeBefore.UtcDateTime - referenceData.MaxPlayoutOffset)
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    foreach (DateTimeOffset removeBefore in result.RemoveBefore)
+                    {
+                        changeCount += await dbContext.PlayoutItems
+                            .Where(pi => pi.PlayoutId == playout.Id)
+                            .Where(pi => pi.Finish < removeBefore.UtcDateTime - referenceData.MaxPlayoutOffset)
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            foreach (DateTimeOffset removeAfter in result.RemoveAfter)
-            {
-                changeCount += await dbContext.PlayoutItems
-                    .Where(pi => pi.PlayoutId == playout.Id)
-                    .Where(pi => pi.Start >= removeAfter.UtcDateTime)
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    foreach (DateTimeOffset removeAfter in result.RemoveAfter)
+                    {
+                        changeCount += await dbContext.PlayoutItems
+                            .Where(pi => pi.PlayoutId == playout.Id)
+                            .Where(pi => pi.Start >= removeAfter.UtcDateTime)
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            if (result.ItemsToRemove.Count > 0)
-            {
-                changeCount += await dbContext.PlayoutItems
-                    .Where(pi => result.ItemsToRemove.Contains(pi.Id))
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    if (result.ItemsToRemove.Count > 0)
+                    {
+                        changeCount += await dbContext.PlayoutItems
+                            .Where(pi => result.ItemsToRemove.Contains(pi.Id))
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            if (result.AddedItems.Count > 0)
-            {
-                changeCount += 1;
-                bool anyWatermarks = result.AddedItems.Any(i =>
-                    i.PlayoutItemWatermarks is not null && i.PlayoutItemWatermarks.Count > 0);
-                bool anyGraphicsElements = result.AddedItems.Any(i =>
-                    i.PlayoutItemGraphicsElements is not null && i.PlayoutItemGraphicsElements.Count > 0);
-                if (anyWatermarks || anyGraphicsElements)
-                {
-                    // need to use slow ef core to also insert watermarks and graphics elements properly
-                    await dbContext.AddRangeAsync(result.AddedItems, cancellationToken);
-                }
-                else
-                {
-                    // no watermarks or graphics, bulk insert is ok
-                    await dbContext.BulkInsertAsync(result.AddedItems, cancellationToken: cancellationToken);
-                }
-            }
+                    if (result.AddedItems.Count > 0)
+                    {
+                        changeCount += 1;
+                        bool anyWatermarks = result.AddedItems.Any(i =>
+                            i.PlayoutItemWatermarks is not null && i.PlayoutItemWatermarks.Count > 0);
+                        bool anyGraphicsElements = result.AddedItems.Any(i =>
+                            i.PlayoutItemGraphicsElements is not null && i.PlayoutItemGraphicsElements.Count > 0);
+                        if (anyWatermarks || anyGraphicsElements)
+                        {
+                            // need to use slow ef core to also insert watermarks and graphics elements properly
+                            await dbContext.AddRangeAsync(result.AddedItems, cancellationToken);
+                        }
+                        else
+                        {
+                            // no watermarks or graphics, bulk insert is ok
+                            await dbContext.BulkInsertAsync(result.AddedItems, cancellationToken: cancellationToken);
+                        }
+                    }
 
-            if (result.HistoryToRemove.Count > 0)
-            {
-                changeCount += await dbContext.PlayoutHistory
-                    .Where(ph => result.HistoryToRemove.Contains(ph.Id))
-                    .ExecuteDeleteAsync(cancellationToken);
-            }
+                    if (result.HistoryToRemove.Count > 0)
+                    {
+                        changeCount += await dbContext.PlayoutHistory
+                            .Where(ph => result.HistoryToRemove.Contains(ph.Id))
+                            .ExecuteDeleteAsync(cancellationToken);
+                    }
 
-            if (result.AddedHistory.Count > 0)
-            {
-                changeCount += 1;
-                await dbContext.BulkInsertAsync(result.AddedHistory, cancellationToken: cancellationToken);
-            }
+                    if (result.AddedHistory.Count > 0)
+                    {
+                        changeCount += 1;
+                        await dbContext.BulkInsertAsync(result.AddedHistory, cancellationToken: cancellationToken);
+                    }
 
-            // let any active segmenter processes know that the playout has been modified
-            // and therefore the segmenter may need to seek into the next item instead of
-            // starting at the beginning (if already working ahead)
-            changeCount += await dbContext.SaveChangesAsync(cancellationToken);
-            bool hasChanges = changeCount > 0;
+                    // let any active segmenter processes know that the playout has been modified
+                    // and therefore the segmenter may need to seek into the next item instead of
+                    // starting at the beginning (if already working ahead)
+                    changeCount += await dbContext.SaveChangesAsync(cancellationToken);
+                    bool hasChanges = changeCount > 0;
 
-            if (request.Mode != PlayoutBuildMode.Continue && hasChanges)
-            {
-                _ffmpegSegmenterService.PlayoutUpdated(referenceData.Channel.Number);
-            }
+                    if (request.Mode != PlayoutBuildMode.Continue && hasChanges)
+                    {
+                        _ffmpegSegmenterService.PlayoutUpdated(referenceData.Channel.Number);
+                    }
 
-            await _workerChannel.WriteAsync(
-                new CheckForOverlappingPlayoutItems(request.PlayoutId),
-                cancellationToken);
+                    await _workerChannel.WriteAsync(
+                        new CheckForOverlappingPlayoutItems(request.PlayoutId),
+                        cancellationToken);
 
-            await _workerChannel.WriteAsync(new InsertPlayoutGaps(request.PlayoutId), cancellationToken);
+                    await _workerChannel.WriteAsync(new InsertPlayoutGaps(request.PlayoutId), cancellationToken);
 
-            string fileName = Path.Combine(FileSystemLayout.ChannelGuideCacheFolder, $"{channelNumber}.xml");
-            if (hasChanges || !File.Exists(fileName) ||
-                playout.ScheduleKind is PlayoutScheduleKind.ExternalJson)
-            {
-                await _workerChannel.WriteAsync(new RefreshChannelData(channelNumber), cancellationToken);
-
-                // refresh guide data for all mirror channels, too
-                List<string> maybeMirrors = await dbContext.Channels
-                    .AsNoTracking()
-                    .Filter(c => c.MirrorSourceChannelId == referenceData.Channel.Id)
-                    .Map(c => c.Number)
-                    .ToListAsync(cancellationToken);
-                foreach (string mirror in maybeMirrors)
-                {
-                    await _workerChannel.WriteAsync(new RefreshChannelData(mirror), cancellationToken);
-                }
-            }
+                    string fileName = Path.Combine(FileSystemLayout.ChannelGuideCacheFolder, $"{channelNumber}.xml");
+                    if (hasChanges || !File.Exists(fileName) ||
+                        playout.ScheduleKind is PlayoutScheduleKind.ExternalJson)
+                    {
+                        await _workerChannel.WriteAsync(new RefreshChannelData(channelNumber), cancellationToken);
+
+                        // refresh guide data for all mirror channels, too
+                        List<string> maybeMirrors = await dbContext.Channels
+                            .AsNoTracking()
+                            .Filter(c => c.MirrorSourceChannelId == referenceData.Channel.Id)
+                            .Map(c => c.Number)
+                            .ToListAsync(cancellationToken);
+                        foreach (string mirror in maybeMirrors)
+                        {
+                            await _workerChannel.WriteAsync(new RefreshChannelData(mirror), cancellationToken);
+                        }
+                    }
+
+                    await _workerChannel.WriteAsync(new ExtractEmbeddedSubtitles(playout.Id), cancellationToken);
 
-            await _workerChannel.WriteAsync(new ExtractEmbeddedSubtitles(playout.Id), cancellationToken);
+                    newBuildStatus.Success = true;
 
-            newBuildStatus.Success = true;
+                    return result;
+                },
+                error =>
+                {
+                    newBuildStatus.Success = false;
+                    newBuildStatus.Message = error.Value;
 
-            return result;
+                    return error;
+                });
         }
         catch (Exception ex) when (ex is TaskCanceledException or OperationCanceledException)
         {
diff --git a/ErsatzTV.Application/Scheduling/Commands/PreviewBlockPlayoutHandler.cs b/ErsatzTV.Application/Scheduling/Commands/PreviewBlockPlayoutHandler.cs
index a956b9c90..4f93633d1 100644
--- a/ErsatzTV.Application/Scheduling/Commands/PreviewBlockPlayoutHandler.cs
+++ b/ErsatzTV.Application/Scheduling/Commands/PreviewBlockPlayoutHandler.cs
@@ -1,4 +1,5 @@
 using System.Diagnostics.CodeAnalysis;
+using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Domain.Scheduling;
 using ErsatzTV.Core.Interfaces.Scheduling;
@@ -68,7 +69,7 @@ public class PreviewBlockPlayoutHandler(
             playout.PlayoutHistory.ToList(),
             TimeSpan.Zero);
 
-        PlayoutBuildResult result =
+        Either<BaseError, PlayoutBuildResult> buildResult =
             await blockPlayoutBuilder.Build(
                 DateTimeOffset.Now,
                 playout,
@@ -76,40 +77,45 @@ public class PreviewBlockPlayoutHandler(
                 PlayoutBuildMode.Reset,
                 cancellationToken);
 
-        // load playout item details for title
-        foreach (PlayoutItem playoutItem in result.AddedItems)
-        {
-            Option<MediaItem> maybeMediaItem = await dbContext.MediaItems
-                .AsNoTracking()
-                .Include(mi => (mi as Movie).MovieMetadata)
-                .Include(mi => (mi as Movie).MediaVersions)
-                .Include(mi => (mi as MusicVideo).MusicVideoMetadata)
-                .Include(mi => (mi as MusicVideo).MediaVersions)
-                .Include(mi => (mi as MusicVideo).Artist)
-                .ThenInclude(mm => mm.ArtistMetadata)
-                .Include(mi => (mi as Episode).EpisodeMetadata)
-                .Include(mi => (mi as Episode).MediaVersions)
-                .Include(mi => (mi as Episode).Season)
-                .ThenInclude(s => s.SeasonMetadata)
-                .Include(mi => (mi as Episode).Season.Show)
-                .ThenInclude(s => s.ShowMetadata)
-                .Include(mi => (mi as OtherVideo).OtherVideoMetadata)
-                .Include(mi => (mi as OtherVideo).MediaVersions)
-                .Include(mi => (mi as Song).SongMetadata)
-                .Include(mi => (mi as Song).MediaVersions)
-                .Include(mi => (mi as Image).ImageMetadata)
-                .Include(mi => (mi as Image).MediaVersions)
-                .Include(mi => (mi as RemoteStream).RemoteStreamMetadata)
-                .Include(mi => (mi as RemoteStream).MediaVersions)
-                .SelectOneAsync(mi => mi.Id, mi => mi.Id == playoutItem.MediaItemId, cancellationToken);
-
-            foreach (MediaItem mediaItem in maybeMediaItem)
+        return await buildResult.MatchAsync(
+            async result =>
             {
-                playoutItem.MediaItem = mediaItem;
-            }
-        }
+                // load playout item details for title
+                foreach (PlayoutItem playoutItem in result.AddedItems)
+                {
+                    Option<MediaItem> maybeMediaItem = await dbContext.MediaItems
+                        .AsNoTracking()
+                        .Include(mi => (mi as Movie).MovieMetadata)
+                        .Include(mi => (mi as Movie).MediaVersions)
+                        .Include(mi => (mi as MusicVideo).MusicVideoMetadata)
+                        .Include(mi => (mi as MusicVideo).MediaVersions)
+                        .Include(mi => (mi as MusicVideo).Artist)
+                        .ThenInclude(mm => mm.ArtistMetadata)
+                        .Include(mi => (mi as Episode).EpisodeMetadata)
+                        .Include(mi => (mi as Episode).MediaVersions)
+                        .Include(mi => (mi as Episode).Season)
+                        .ThenInclude(s => s.SeasonMetadata)
+                        .Include(mi => (mi as Episode).Season.Show)
+                        .ThenInclude(s => s.ShowMetadata)
+                        .Include(mi => (mi as OtherVideo).OtherVideoMetadata)
+                        .Include(mi => (mi as OtherVideo).MediaVersions)
+                        .Include(mi => (mi as Song).SongMetadata)
+                        .Include(mi => (mi as Song).MediaVersions)
+                        .Include(mi => (mi as Image).ImageMetadata)
+                        .Include(mi => (mi as Image).MediaVersions)
+                        .Include(mi => (mi as RemoteStream).RemoteStreamMetadata)
+                        .Include(mi => (mi as RemoteStream).MediaVersions)
+                        .SelectOneAsync(mi => mi.Id, mi => mi.Id == playoutItem.MediaItemId, cancellationToken);
 
-        return result.AddedItems.Map(Mapper.ProjectToViewModel).ToList();
+                    foreach (MediaItem mediaItem in maybeMediaItem)
+                    {
+                        playoutItem.MediaItem = mediaItem;
+                    }
+                }
+
+                return result.AddedItems.Map(Mapper.ProjectToViewModel).ToList();
+            },
+            _ => []);
     }
 
     private static Block MapToBlock(ReplaceBlockItems request) =>
diff --git a/ErsatzTV.Core.Tests/Scheduling/BlockScheduling/BlockPlayoutBuilderTests.cs b/ErsatzTV.Core.Tests/Scheduling/BlockScheduling/BlockPlayoutBuilderTests.cs
index f552ed870..5ca98bc36 100644
--- a/ErsatzTV.Core.Tests/Scheduling/BlockScheduling/BlockPlayoutBuilderTests.cs
+++ b/ErsatzTV.Core.Tests/Scheduling/BlockScheduling/BlockPlayoutBuilderTests.cs
@@ -150,18 +150,22 @@ public class BlockPlayoutBuilderTests
                 [],
                 TimeSpan.Zero);
 
-            PlayoutBuildResult result = await builder.Build(
+            Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
                 now,
                 playout,
                 referenceData,
                 PlayoutBuildMode.Reset,
                 cancellationToken);
 
-            // this test only cares about "today"
-            result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
+            buildResult.IsRight.ShouldBeTrue();
+            foreach (var result in buildResult.RightToSeq())
+            {
+                // this test only cares about "today"
+                result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
 
-            result.AddedItems.Count.ShouldBe(1);
-            result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+                result.AddedItems.Count.ShouldBe(1);
+                result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+            }
         }
 
         [Test]
@@ -293,18 +297,22 @@ public class BlockPlayoutBuilderTests
                 [],
                 TimeSpan.Zero);
 
-            PlayoutBuildResult result = await builder.Build(
+            Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
                 now,
                 playout,
                 referenceData,
                 PlayoutBuildMode.Reset,
                 cancellationToken);
 
-            // this test only cares about "today"
-            result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
+            buildResult.IsRight.ShouldBeTrue();
+            foreach (var result in buildResult.RightToSeq())
+            {
+                // this test only cares about "today"
+                result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
 
-            result.AddedItems.Count.ShouldBe(1);
-            result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+                result.AddedItems.Count.ShouldBe(1);
+                result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+            }
         }
 
         [Test]
@@ -459,18 +467,22 @@ public class BlockPlayoutBuilderTests
                 [],
                 TimeSpan.Zero);
 
-            PlayoutBuildResult result = await builder.Build(
+            Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
                 now,
                 playout,
                 referenceData,
                 PlayoutBuildMode.Reset,
                 cancellationToken);
 
-            // this test only cares about "today"
-            result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
+            buildResult.IsRight.ShouldBeTrue();
+            foreach (var result in buildResult.RightToSeq())
+            {
+                // this test only cares about "today"
+                result.AddedItems.RemoveAll(i => i.StartOffset.Date > now.Date);
 
-            result.AddedItems.Count.ShouldBe(1);
-            result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+                result.AddedItems.Count.ShouldBe(1);
+                result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(9));
+            }
         }
     }
 
diff --git a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ContinuePlayoutTests.cs b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ContinuePlayoutTests.cs
index b432f5d47..3571032d7 100644
--- a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ContinuePlayoutTests.cs
+++ b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ContinuePlayoutTests.cs
@@ -28,7 +28,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -37,8 +37,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
 
@@ -48,7 +52,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -57,9 +61,13 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result2.AddedItems.Count.ShouldBe(1);
-        result2.AddedItems[0].StartOffset.ShouldBe(finish);
-        result2.AddedItems[0].MediaItemId.ShouldBe(2);
+        buildResult2.IsRight.ShouldBeTrue();
+        foreach (var result2 in buildResult2.RightToSeq())
+        {
+            result2.AddedItems.Count.ShouldBe(1);
+            result2.AddedItems[0].StartOffset.ShouldBe(finish);
+            result2.AddedItems[0].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(12));
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -80,7 +88,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -89,8 +97,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -99,7 +111,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(12);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -108,11 +120,15 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result2.AddedItems.Count.ShouldBe(2);
-        result2.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result2.AddedItems[0].MediaItemId.ShouldBe(2);
-        result2.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result2.AddedItems[1].MediaItemId.ShouldBe(1);
+        buildResult2.IsRight.ShouldBeTrue();
+        foreach (var result2 in buildResult2.RightToSeq())
+        {
+            result2.AddedItems.Count.ShouldBe(2);
+            result2.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result2.AddedItems[0].MediaItemId.ShouldBe(2);
+            result2.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result2.AddedItems[1].MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(18));
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -133,7 +149,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromDays(1);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -142,8 +158,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(4);
-        result.AddedItems.Map(i => i.MediaItemId).ToList().ShouldBe([1, 2, 1, 2]);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(4);
+            result.AddedItems.Map(i => i.MediaItemId).ToList().ShouldBe([1, 2, 1, 2]);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -177,7 +197,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromDays(1);
 
-        result = await builder.Build(
+        buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -186,9 +206,13 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems[0].StartOffset.ShouldBe(finish);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(finish);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(30));
 
@@ -199,7 +223,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start3 = HoursAfterMidnight(2);
         DateTimeOffset finish3 = start3 + TimeSpan.FromDays(1);
 
-        result = await builder.Build(
+        buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -208,7 +232,11 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish3,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(0);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(0);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(30));
 
@@ -231,7 +259,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -240,7 +268,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+        }
+
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
         playout.ProgramScheduleAnchors.Head().EnumeratorState.Seed.ShouldBeGreaterThan(0);
 
@@ -251,7 +284,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(0);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -281,7 +314,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0).AddSeconds(5);
         DateTimeOffset finish = start + TimeSpan.FromDays(2);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -290,7 +323,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(53);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(53);
+        }
+
         playout.ProgramScheduleAnchors.Count.ShouldBe(2);
 
         playout.ProgramScheduleAnchors.All(x => x.AnchorDate is not null).ShouldBeTrue();
@@ -318,7 +356,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = start.AddHours(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromDays(2);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -350,7 +388,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -359,7 +397,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+        }
+
         playout.ProgramScheduleAnchors.Count.ShouldBe(2);
         PlayoutProgramScheduleAnchor primaryAnchor =
             playout.ProgramScheduleAnchors.First(a => a.SmartCollectionId == 1);
@@ -371,7 +414,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(0);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -402,7 +445,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0).AddSeconds(5);
         DateTimeOffset finish = start + TimeSpan.FromDays(2);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -411,7 +454,12 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(53);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(53);
+        }
+
         playout.ProgramScheduleAnchors.Count.ShouldBe(4);
 
         playout.ProgramScheduleAnchors.All(x => x.AnchorDate is not null).ShouldBeTrue();
@@ -429,7 +477,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             DateTimeOffset start2 = start.AddHours(i);
             DateTimeOffset finish2 = start2 + TimeSpan.FromDays(2);
 
-            PlayoutBuildResult result2 = await builder.Build(
+            Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
                 playout,
                 referenceData,
                 PlayoutBuildResult.Empty,
@@ -555,7 +603,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(32);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -564,20 +612,24 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(5);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(5);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
 
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(31));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(31));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.InFlood.ShouldBeTrue();
 
@@ -677,7 +729,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(5);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -686,17 +738,21 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(4);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(4);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[1].MediaItemId.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[1].MediaItemId.ShouldBe(1);
 
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[2].MediaItemId.ShouldBe(2);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
-        result.AddedItems[3].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[2].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
+            result.AddedItems[3].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(1);
         playout.Anchor.MultipleRemaining.ShouldBe(1);
@@ -798,7 +854,7 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             rerunHelper,
             Logger);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -807,19 +863,23 @@ public class ContinuePlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(5);
-
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[1].MediaItemId.ShouldBe(1);
-
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[2].MediaItemId.ShouldBe(2);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
-        result.AddedItems[3].MediaItemId.ShouldBe(2);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(5);
+
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[1].MediaItemId.ShouldBe(1);
+
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[2].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
+            result.AddedItems[3].MediaItemId.ShouldBe(2);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(0);
         playout.Anchor.DurationFinish.ShouldBeNull();
diff --git a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/NewPlayoutTests.cs b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/NewPlayoutTests.cs
index db8e17bb9..17e14d416 100644
--- a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/NewPlayoutTests.cs
+++ b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/NewPlayoutTests.cs
@@ -26,10 +26,10 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         (PlayoutBuilder builder, Playout playout, PlayoutReferenceData referenceData) =
             TestDataFloodForItems(mediaItems, PlaybackOrder.Random);
 
-        PlayoutBuildResult result =
+        Either<BaseError, PlayoutBuildResult> buildResult =
             await builder.Build(DateTimeOffset.Now, playout, referenceData, PlayoutBuildMode.Reset, CancellationToken);
 
-        result.AddedItems.ShouldBeEmpty();
+        buildResult.IsLeft.ShouldBeTrue();
     }
 
     [Test]
@@ -46,7 +46,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -55,10 +55,14 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(2);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(start + TimeSpan.FromHours(6));
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(2);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(start + TimeSpan.FromHours(6));
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(6));
     }
@@ -83,10 +87,10 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         (PlayoutBuilder builder, Playout playout, PlayoutReferenceData referenceData) =
             TestDataFloodForItems(mediaItems, PlaybackOrder.Random, configRepo);
 
-        PlayoutBuildResult result =
+        Either<BaseError, PlayoutBuildResult> buildResult =
             await builder.Build(DateTimeOffset.Now, playout, referenceData, PlayoutBuildMode.Reset, CancellationToken);
 
-        result.AddedItems.ShouldBeEmpty();
+        buildResult.IsLeft.ShouldBeTrue();
     }
 
     [Test]
@@ -112,7 +116,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -121,10 +125,14 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(2);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(2);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -149,10 +157,10 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         (PlayoutBuilder builder, Playout playout, PlayoutReferenceData referenceData) =
             TestDataFloodForItems(mediaItems, PlaybackOrder.Random, configRepo);
 
-        PlayoutBuildResult result =
+        Either<BaseError, PlayoutBuildResult> buildResult =
             await builder.Build(DateTimeOffset.Now, playout, referenceData, PlayoutBuildMode.Reset, CancellationToken);
 
-        result.AddedItems.ShouldBeEmpty();
+        buildResult.IsLeft.ShouldBeTrue();
     }
 
     [Test]
@@ -178,7 +186,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -187,10 +195,14 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(2);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(2);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -217,7 +229,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -226,9 +238,13 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -255,7 +271,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -264,9 +280,13 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -284,7 +304,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -293,9 +313,13 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().StartOffset.ShouldBe(start);
-        result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().StartOffset.ShouldBe(start);
+            result.AddedItems.Head().FinishOffset.ShouldBe(finish);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -314,7 +338,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(1);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -323,10 +347,14 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(2);
-        result.AddedItems[0].StartOffset.ShouldBe(midnight);
-        result.AddedItems[1].StartOffset.ShouldBe(midnight + TimeSpan.FromHours(6));
-        result.AddedItems[1].FinishOffset.ShouldBe(midnight + TimeSpan.FromHours(12));
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(2);
+            result.AddedItems[0].StartOffset.ShouldBe(midnight);
+            result.AddedItems[1].StartOffset.ShouldBe(midnight + TimeSpan.FromHours(6));
+            result.AddedItems[1].FinishOffset.ShouldBe(midnight + TimeSpan.FromHours(12));
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(midnight + TimeSpan.FromHours(12));
     }
@@ -345,7 +373,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(4);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -354,15 +382,19 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(4);
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(2);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(4);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(4));
     }
@@ -381,7 +413,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -390,8 +422,12 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
 
@@ -401,7 +437,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -410,9 +446,13 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result2.AddedItems.Count.ShouldBe(1);
-        result2.AddedItems[0].StartOffset.ShouldBe(finish);
-        result2.AddedItems[0].MediaItemId.ShouldBe(2);
+        buildResult2.IsRight.ShouldBeTrue();
+        foreach (var result2 in buildResult2.RightToSeq())
+        {
+            result2.AddedItems.Count.ShouldBe(1);
+            result2.AddedItems[0].StartOffset.ShouldBe(finish);
+            result2.AddedItems[0].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(12));
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -433,7 +473,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -442,8 +482,12 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(1);
-        result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(1);
+            result.AddedItems.Head().MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -452,7 +496,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(1);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(12);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -461,11 +505,15 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result2.AddedItems.Count.ShouldBe(2);
-        result2.AddedItems[0].StartOffset.ShouldBe(finish);
-        result2.AddedItems[0].MediaItemId.ShouldBe(2);
-        result2.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result2.AddedItems[1].MediaItemId.ShouldBe(1);
+        buildResult2.IsRight.ShouldBeTrue();
+        foreach (var result2 in buildResult2.RightToSeq())
+        {
+            result2.AddedItems.Count.ShouldBe(2);
+            result2.AddedItems[0].StartOffset.ShouldBe(finish);
+            result2.AddedItems[0].MediaItemId.ShouldBe(2);
+            result2.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result2.AddedItems[1].MediaItemId.ShouldBe(1);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(18));
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -564,7 +612,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -573,17 +621,21 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(5);
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(5);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -680,7 +732,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(30);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -689,63 +741,67 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(28);
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result.AddedItems[5].MediaItemId.ShouldBe(1);
-        result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(7));
-        result.AddedItems[6].MediaItemId.ShouldBe(2);
-        result.AddedItems[7].StartOffset.ShouldBe(start + TimeSpan.FromHours(8));
-        result.AddedItems[7].MediaItemId.ShouldBe(1);
-        result.AddedItems[8].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
-        result.AddedItems[8].MediaItemId.ShouldBe(2);
-        result.AddedItems[9].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
-        result.AddedItems[9].MediaItemId.ShouldBe(1);
-        result.AddedItems[10].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
-        result.AddedItems[10].MediaItemId.ShouldBe(2);
-        result.AddedItems[11].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result.AddedItems[11].MediaItemId.ShouldBe(1);
-        result.AddedItems[12].StartOffset.ShouldBe(start + TimeSpan.FromHours(13));
-        result.AddedItems[12].MediaItemId.ShouldBe(2);
-        result.AddedItems[13].StartOffset.ShouldBe(start + TimeSpan.FromHours(14));
-        result.AddedItems[13].MediaItemId.ShouldBe(1);
-        result.AddedItems[14].StartOffset.ShouldBe(start + TimeSpan.FromHours(15));
-        result.AddedItems[14].MediaItemId.ShouldBe(2);
-        result.AddedItems[15].StartOffset.ShouldBe(start + TimeSpan.FromHours(16));
-        result.AddedItems[15].MediaItemId.ShouldBe(1);
-        result.AddedItems[16].StartOffset.ShouldBe(start + TimeSpan.FromHours(17));
-        result.AddedItems[16].MediaItemId.ShouldBe(2);
-        result.AddedItems[17].StartOffset.ShouldBe(start + TimeSpan.FromHours(18));
-        result.AddedItems[17].MediaItemId.ShouldBe(1);
-        result.AddedItems[18].StartOffset.ShouldBe(start + TimeSpan.FromHours(19));
-        result.AddedItems[18].MediaItemId.ShouldBe(2);
-        result.AddedItems[19].StartOffset.ShouldBe(start + TimeSpan.FromHours(20));
-        result.AddedItems[19].MediaItemId.ShouldBe(1);
-        result.AddedItems[20].StartOffset.ShouldBe(start + TimeSpan.FromHours(21));
-        result.AddedItems[20].MediaItemId.ShouldBe(2);
-        result.AddedItems[21].StartOffset.ShouldBe(start + TimeSpan.FromHours(22));
-        result.AddedItems[21].MediaItemId.ShouldBe(1);
-        result.AddedItems[22].StartOffset.ShouldBe(start + TimeSpan.FromHours(23));
-        result.AddedItems[22].MediaItemId.ShouldBe(2);
-        result.AddedItems[23].StartOffset.ShouldBe(start + TimeSpan.FromHours(24));
-        result.AddedItems[23].MediaItemId.ShouldBe(1);
-        result.AddedItems[24].StartOffset.ShouldBe(start + TimeSpan.FromHours(25));
-        result.AddedItems[24].MediaItemId.ShouldBe(2);
-        result.AddedItems[25].StartOffset.ShouldBe(start + TimeSpan.FromHours(26));
-        result.AddedItems[25].MediaItemId.ShouldBe(1);
-        result.AddedItems[26].StartOffset.ShouldBe(start + TimeSpan.FromHours(27));
-        result.AddedItems[26].MediaItemId.ShouldBe(3);
-        result.AddedItems[27].StartOffset.ShouldBe(start + TimeSpan.FromHours(29));
-        result.AddedItems[27].MediaItemId.ShouldBe(2);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(28);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result.AddedItems[5].MediaItemId.ShouldBe(1);
+            result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(7));
+            result.AddedItems[6].MediaItemId.ShouldBe(2);
+            result.AddedItems[7].StartOffset.ShouldBe(start + TimeSpan.FromHours(8));
+            result.AddedItems[7].MediaItemId.ShouldBe(1);
+            result.AddedItems[8].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
+            result.AddedItems[8].MediaItemId.ShouldBe(2);
+            result.AddedItems[9].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
+            result.AddedItems[9].MediaItemId.ShouldBe(1);
+            result.AddedItems[10].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
+            result.AddedItems[10].MediaItemId.ShouldBe(2);
+            result.AddedItems[11].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result.AddedItems[11].MediaItemId.ShouldBe(1);
+            result.AddedItems[12].StartOffset.ShouldBe(start + TimeSpan.FromHours(13));
+            result.AddedItems[12].MediaItemId.ShouldBe(2);
+            result.AddedItems[13].StartOffset.ShouldBe(start + TimeSpan.FromHours(14));
+            result.AddedItems[13].MediaItemId.ShouldBe(1);
+            result.AddedItems[14].StartOffset.ShouldBe(start + TimeSpan.FromHours(15));
+            result.AddedItems[14].MediaItemId.ShouldBe(2);
+            result.AddedItems[15].StartOffset.ShouldBe(start + TimeSpan.FromHours(16));
+            result.AddedItems[15].MediaItemId.ShouldBe(1);
+            result.AddedItems[16].StartOffset.ShouldBe(start + TimeSpan.FromHours(17));
+            result.AddedItems[16].MediaItemId.ShouldBe(2);
+            result.AddedItems[17].StartOffset.ShouldBe(start + TimeSpan.FromHours(18));
+            result.AddedItems[17].MediaItemId.ShouldBe(1);
+            result.AddedItems[18].StartOffset.ShouldBe(start + TimeSpan.FromHours(19));
+            result.AddedItems[18].MediaItemId.ShouldBe(2);
+            result.AddedItems[19].StartOffset.ShouldBe(start + TimeSpan.FromHours(20));
+            result.AddedItems[19].MediaItemId.ShouldBe(1);
+            result.AddedItems[20].StartOffset.ShouldBe(start + TimeSpan.FromHours(21));
+            result.AddedItems[20].MediaItemId.ShouldBe(2);
+            result.AddedItems[21].StartOffset.ShouldBe(start + TimeSpan.FromHours(22));
+            result.AddedItems[21].MediaItemId.ShouldBe(1);
+            result.AddedItems[22].StartOffset.ShouldBe(start + TimeSpan.FromHours(23));
+            result.AddedItems[22].MediaItemId.ShouldBe(2);
+            result.AddedItems[23].StartOffset.ShouldBe(start + TimeSpan.FromHours(24));
+            result.AddedItems[23].MediaItemId.ShouldBe(1);
+            result.AddedItems[24].StartOffset.ShouldBe(start + TimeSpan.FromHours(25));
+            result.AddedItems[24].MediaItemId.ShouldBe(2);
+            result.AddedItems[25].StartOffset.ShouldBe(start + TimeSpan.FromHours(26));
+            result.AddedItems[25].MediaItemId.ShouldBe(1);
+            result.AddedItems[26].StartOffset.ShouldBe(start + TimeSpan.FromHours(27));
+            result.AddedItems[26].MediaItemId.ShouldBe(3);
+            result.AddedItems[27].StartOffset.ShouldBe(start + TimeSpan.FromHours(29));
+            result.AddedItems[27].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(30));
     }
@@ -847,7 +903,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(7);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -856,22 +912,26 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[4].MediaItemId.ShouldBe(4);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[4].MediaItemId.ShouldBe(4);
 
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result.AddedItems[5].MediaItemId.ShouldBe(2);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result.AddedItems[5].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -973,7 +1033,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(7);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -982,22 +1042,26 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(50));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(50 + 60));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(50));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(50 + 60));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[4].MediaItemId.ShouldBe(4);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[4].MediaItemId.ShouldBe(4);
 
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result.AddedItems[5].MediaItemId.ShouldBe(2);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result.AddedItems[5].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(finish);
     }
@@ -1098,7 +1162,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(24);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1107,21 +1171,25 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
-
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(7));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(8));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
-        result.AddedItems[3].MediaItemId.ShouldBe(2);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
-        result.AddedItems[4].MediaItemId.ShouldBe(1);
-
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result.AddedItems[5].MediaItemId.ShouldBe(3);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromHours(7));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(8));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(9));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(10));
+            result.AddedItems[3].MediaItemId.ShouldBe(2);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(11));
+            result.AddedItems[4].MediaItemId.ShouldBe(1);
+
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result.AddedItems[5].MediaItemId.ShouldBe(3);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(31));
     }
@@ -1224,7 +1292,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1233,25 +1301,29 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(7);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(7);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
 
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(3);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(3);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(2.75));
-        result.AddedItems[3].MediaItemId.ShouldBe(1);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(3.75));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(2.75));
+            result.AddedItems[3].MediaItemId.ShouldBe(1);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(3.75));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
 
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(4.75));
-        result.AddedItems[5].MediaItemId.ShouldBe(1);
-        result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(5.75));
-        result.AddedItems[6].MediaItemId.ShouldBe(2);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(4.75));
+            result.AddedItems[5].MediaItemId.ShouldBe(1);
+            result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(5.75));
+            result.AddedItems[6].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(6.75));
     }
@@ -1355,7 +1427,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1364,23 +1436,27 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
 
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(3);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(3);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(2.75));
-        result.AddedItems[3].MediaItemId.ShouldBe(1);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(3.75));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(2.75));
+            result.AddedItems[3].MediaItemId.ShouldBe(1);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(3.75));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
 
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(4.75));
-        result.AddedItems[5].MediaItemId.ShouldBe(4);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(4.75));
+            result.AddedItems[5].MediaItemId.ShouldBe(4);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(start + TimeSpan.FromHours(6.25));
     }
@@ -1486,7 +1562,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(5);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1495,19 +1571,23 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(5);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(5);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(3);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(3);
 
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(4);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
-        result.AddedItems[4].MediaItemId.ShouldBe(5);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(4);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
+            result.AddedItems[4].MediaItemId.ShouldBe(5);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(0);
         playout.Anchor.MultipleRemaining.ShouldBeNull();
@@ -1626,7 +1706,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1635,35 +1715,39 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(12);
-
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(0));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(55));
-        result.AddedItems[1].MediaItemId.ShouldBe(1);
-        result.AddedItems[2].StartOffset.ShouldBe(start + new TimeSpan(1, 50, 0));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-
-        result.AddedItems[3].StartOffset.ShouldBe(start + new TimeSpan(2, 45, 0));
-        result.AddedItems[3].MediaItemId.ShouldBe(3);
-        result.AddedItems[4].StartOffset.ShouldBe(start + new TimeSpan(2, 50, 0));
-        result.AddedItems[4].MediaItemId.ShouldBe(3);
-        result.AddedItems[5].StartOffset.ShouldBe(start + new TimeSpan(2, 55, 0));
-        result.AddedItems[5].MediaItemId.ShouldBe(3);
-
-        result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[6].MediaItemId.ShouldBe(2);
-        result.AddedItems[7].StartOffset.ShouldBe(start + new TimeSpan(3, 55, 0));
-        result.AddedItems[7].MediaItemId.ShouldBe(2);
-        result.AddedItems[8].StartOffset.ShouldBe(start + new TimeSpan(4, 50, 0));
-        result.AddedItems[8].MediaItemId.ShouldBe(2);
-
-        result.AddedItems[9].StartOffset.ShouldBe(start + new TimeSpan(5, 45, 0));
-        result.AddedItems[9].MediaItemId.ShouldBe(3);
-        result.AddedItems[10].StartOffset.ShouldBe(start + new TimeSpan(5, 50, 0));
-        result.AddedItems[10].MediaItemId.ShouldBe(3);
-        result.AddedItems[11].StartOffset.ShouldBe(start + new TimeSpan(5, 55, 0));
-        result.AddedItems[11].MediaItemId.ShouldBe(3);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(12);
+
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(0));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(55));
+            result.AddedItems[1].MediaItemId.ShouldBe(1);
+            result.AddedItems[2].StartOffset.ShouldBe(start + new TimeSpan(1, 50, 0));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+
+            result.AddedItems[3].StartOffset.ShouldBe(start + new TimeSpan(2, 45, 0));
+            result.AddedItems[3].MediaItemId.ShouldBe(3);
+            result.AddedItems[4].StartOffset.ShouldBe(start + new TimeSpan(2, 50, 0));
+            result.AddedItems[4].MediaItemId.ShouldBe(3);
+            result.AddedItems[5].StartOffset.ShouldBe(start + new TimeSpan(2, 55, 0));
+            result.AddedItems[5].MediaItemId.ShouldBe(3);
+
+            result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[6].MediaItemId.ShouldBe(2);
+            result.AddedItems[7].StartOffset.ShouldBe(start + new TimeSpan(3, 55, 0));
+            result.AddedItems[7].MediaItemId.ShouldBe(2);
+            result.AddedItems[8].StartOffset.ShouldBe(start + new TimeSpan(4, 50, 0));
+            result.AddedItems[8].MediaItemId.ShouldBe(2);
+
+            result.AddedItems[9].StartOffset.ShouldBe(start + new TimeSpan(5, 45, 0));
+            result.AddedItems[9].MediaItemId.ShouldBe(3);
+            result.AddedItems[10].StartOffset.ShouldBe(start + new TimeSpan(5, 50, 0));
+            result.AddedItems[10].MediaItemId.ShouldBe(3);
+            result.AddedItems[11].StartOffset.ShouldBe(start + new TimeSpan(5, 55, 0));
+            result.AddedItems[11].MediaItemId.ShouldBe(3);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(0);
         playout.Anchor.DurationFinish.ShouldBeNull();
@@ -1759,7 +1843,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(1);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1768,12 +1852,16 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(2);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(2);
 
-        result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(0));
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(61));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[0].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(0));
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromMinutes(61));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(0);
         playout.Anchor.DurationFinish.ShouldBeNull();
@@ -1858,7 +1946,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1867,20 +1955,24 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
-
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].MediaItemId.ShouldBe(2);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
-        result.AddedItems[1].MediaItemId.ShouldBe(4);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
-        result.AddedItems[2].MediaItemId.ShouldBe(2);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
-        result.AddedItems[3].MediaItemId.ShouldBe(4);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
-        result.AddedItems[5].MediaItemId.ShouldBe(4);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].MediaItemId.ShouldBe(2);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(1));
+            result.AddedItems[1].MediaItemId.ShouldBe(4);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(2));
+            result.AddedItems[2].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(3));
+            result.AddedItems[3].MediaItemId.ShouldBe(4);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(4));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(5));
+            result.AddedItems[5].MediaItemId.ShouldBe(4);
+        }
 
         playout.Anchor.ScheduleItemsEnumeratorState.Index.ShouldBe(0);
         playout.Anchor.DurationFinish.ShouldBeNull();
@@ -1902,7 +1994,7 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromDays(2);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -1911,31 +2003,35 @@ public class NewPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(8);
-        result.AddedItems[0].MediaItemId.ShouldBe(1);
-        result.AddedItems[0].StartOffset.ShouldBe(start);
-        result.AddedItems[0].FinishOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result.AddedItems[1].MediaItemId.ShouldBe(2);
-        result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
-        result.AddedItems[1].FinishOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result.AddedItems[2].MediaItemId.ShouldBe(3);
-        result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
-        result.AddedItems[2].FinishOffset.ShouldBe(start + TimeSpan.FromHours(18));
-        result.AddedItems[3].MediaItemId.ShouldBe(1);
-        result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(18));
-        result.AddedItems[3].FinishOffset.ShouldBe(start + TimeSpan.FromHours(24));
-        result.AddedItems[4].MediaItemId.ShouldBe(2);
-        result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(24));
-        result.AddedItems[4].FinishOffset.ShouldBe(start + TimeSpan.FromHours(30));
-        result.AddedItems[5].MediaItemId.ShouldBe(3);
-        result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(30));
-        result.AddedItems[5].FinishOffset.ShouldBe(start + TimeSpan.FromHours(36));
-        result.AddedItems[6].MediaItemId.ShouldBe(1);
-        result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(36));
-        result.AddedItems[6].FinishOffset.ShouldBe(start + TimeSpan.FromHours(42));
-        result.AddedItems[7].MediaItemId.ShouldBe(2);
-        result.AddedItems[7].StartOffset.ShouldBe(start + TimeSpan.FromHours(42));
-        result.AddedItems[7].FinishOffset.ShouldBe(start + TimeSpan.FromHours(48));
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(8);
+            result.AddedItems[0].MediaItemId.ShouldBe(1);
+            result.AddedItems[0].StartOffset.ShouldBe(start);
+            result.AddedItems[0].FinishOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result.AddedItems[1].MediaItemId.ShouldBe(2);
+            result.AddedItems[1].StartOffset.ShouldBe(start + TimeSpan.FromHours(6));
+            result.AddedItems[1].FinishOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result.AddedItems[2].MediaItemId.ShouldBe(3);
+            result.AddedItems[2].StartOffset.ShouldBe(start + TimeSpan.FromHours(12));
+            result.AddedItems[2].FinishOffset.ShouldBe(start + TimeSpan.FromHours(18));
+            result.AddedItems[3].MediaItemId.ShouldBe(1);
+            result.AddedItems[3].StartOffset.ShouldBe(start + TimeSpan.FromHours(18));
+            result.AddedItems[3].FinishOffset.ShouldBe(start + TimeSpan.FromHours(24));
+            result.AddedItems[4].MediaItemId.ShouldBe(2);
+            result.AddedItems[4].StartOffset.ShouldBe(start + TimeSpan.FromHours(24));
+            result.AddedItems[4].FinishOffset.ShouldBe(start + TimeSpan.FromHours(30));
+            result.AddedItems[5].MediaItemId.ShouldBe(3);
+            result.AddedItems[5].StartOffset.ShouldBe(start + TimeSpan.FromHours(30));
+            result.AddedItems[5].FinishOffset.ShouldBe(start + TimeSpan.FromHours(36));
+            result.AddedItems[6].MediaItemId.ShouldBe(1);
+            result.AddedItems[6].StartOffset.ShouldBe(start + TimeSpan.FromHours(36));
+            result.AddedItems[6].FinishOffset.ShouldBe(start + TimeSpan.FromHours(42));
+            result.AddedItems[7].MediaItemId.ShouldBe(2);
+            result.AddedItems[7].StartOffset.ShouldBe(start + TimeSpan.FromHours(42));
+            result.AddedItems[7].FinishOffset.ShouldBe(start + TimeSpan.FromHours(48));
+        }
 
         playout.ProgramScheduleAnchors.Count.ShouldBe(2);
         playout.ProgramScheduleAnchors.Count(a => a.EnumeratorState.Index == 4 % 3).ShouldBe(1);
diff --git a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/RefreshPlayoutTests.cs b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/RefreshPlayoutTests.cs
index ac1af8571..0332a1e51 100644
--- a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/RefreshPlayoutTests.cs
+++ b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/RefreshPlayoutTests.cs
@@ -116,7 +116,7 @@ public class RefreshPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(24);
         DateTimeOffset finish = start + TimeSpan.FromDays(1);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -125,19 +125,24 @@ public class RefreshPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(4);
-        result.AddedItems[0].MediaItemId.ShouldBe(2);
-        result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.Zero);
-        result.AddedItems[0].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(6));
-        result.AddedItems[1].MediaItemId.ShouldBe(3);
-        result.AddedItems[1].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(6));
-        result.AddedItems[1].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(12));
-        result.AddedItems[2].MediaItemId.ShouldBe(1);
-        result.AddedItems[2].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(12));
-        result.AddedItems[2].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(18));
-        result.AddedItems[3].MediaItemId.ShouldBe(2);
-        result.AddedItems[3].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(18));
-        result.AddedItems[3].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.Zero);
+        buildResult.IsRight.ShouldBeTrue();
+
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(4);
+            result.AddedItems[0].MediaItemId.ShouldBe(2);
+            result.AddedItems[0].StartOffset.TimeOfDay.ShouldBe(TimeSpan.Zero);
+            result.AddedItems[0].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(6));
+            result.AddedItems[1].MediaItemId.ShouldBe(3);
+            result.AddedItems[1].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(6));
+            result.AddedItems[1].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(12));
+            result.AddedItems[2].MediaItemId.ShouldBe(1);
+            result.AddedItems[2].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(12));
+            result.AddedItems[2].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(18));
+            result.AddedItems[3].MediaItemId.ShouldBe(2);
+            result.AddedItems[3].StartOffset.TimeOfDay.ShouldBe(TimeSpan.FromHours(18));
+            result.AddedItems[3].FinishOffset.TimeOfDay.ShouldBe(TimeSpan.Zero);
+        }
 
         playout.Anchor.NextStartOffset.ShouldBe(HoursAfterMidnight(48));
     }
diff --git a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ResetPlayoutTests.cs b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ResetPlayoutTests.cs
index 733441dbd..de792ea29 100644
--- a/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ResetPlayoutTests.cs
+++ b/ErsatzTV.Core.Tests/Scheduling/ClassicScheduling/ResetPlayoutTests.cs
@@ -26,7 +26,7 @@ public class ResetPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start = HoursAfterMidnight(0);
         DateTimeOffset finish = start + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -35,7 +35,12 @@ public class ResetPlayoutTests : PlayoutBuilderTestBase
             finish,
             CancellationToken);
 
-        result.AddedItems.Count.ShouldBe(6);
+        buildResult.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+        }
+
         playout.Anchor.NextStartOffset.ShouldBe(finish);
 
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
@@ -46,7 +51,7 @@ public class ResetPlayoutTests : PlayoutBuilderTestBase
         DateTimeOffset start2 = HoursAfterMidnight(0);
         DateTimeOffset finish2 = start2 + TimeSpan.FromHours(6);
 
-        PlayoutBuildResult result2 = await builder.Build(
+        Either<BaseError, PlayoutBuildResult> buildResult2 = await builder.Build(
             playout,
             referenceData,
             PlayoutBuildResult.Empty,
@@ -55,7 +60,12 @@ public class ResetPlayoutTests : PlayoutBuilderTestBase
             finish2,
             CancellationToken);
 
-        result2.AddedItems.Count.ShouldBe(6);
+        buildResult2.IsRight.ShouldBeTrue();
+        foreach (var result in buildResult2.RightToSeq())
+        {
+            result.AddedItems.Count.ShouldBe(6);
+        }
+
         playout.Anchor.NextStartOffset.ShouldBe(finish);
 
         playout.ProgramScheduleAnchors.Count.ShouldBe(1);
diff --git a/ErsatzTV.Core/Interfaces/Scheduling/IBlockPlayoutBuilder.cs b/ErsatzTV.Core/Interfaces/Scheduling/IBlockPlayoutBuilder.cs
index 6779f6a1e..c7b3fb8c7 100644
--- a/ErsatzTV.Core/Interfaces/Scheduling/IBlockPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Interfaces/Scheduling/IBlockPlayoutBuilder.cs
@@ -5,7 +5,7 @@ namespace ErsatzTV.Core.Interfaces.Scheduling;
 
 public interface IBlockPlayoutBuilder
 {
-    Task<PlayoutBuildResult> Build(
+    Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
diff --git a/ErsatzTV.Core/Interfaces/Scheduling/IPlayoutBuilder.cs b/ErsatzTV.Core/Interfaces/Scheduling/IPlayoutBuilder.cs
index 0426b5ff7..10cf4f663 100644
--- a/ErsatzTV.Core/Interfaces/Scheduling/IPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Interfaces/Scheduling/IPlayoutBuilder.cs
@@ -8,7 +8,7 @@ public interface IPlayoutBuilder
     bool TrimStart { get; set; }
     Playlist DebugPlaylist { get; set; }
 
-    Task<PlayoutBuildResult> Build(
+    Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
diff --git a/ErsatzTV.Core/Interfaces/Scheduling/IScriptedPlayoutBuilder.cs b/ErsatzTV.Core/Interfaces/Scheduling/IScriptedPlayoutBuilder.cs
index fdf284ae6..f99658632 100644
--- a/ErsatzTV.Core/Interfaces/Scheduling/IScriptedPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Interfaces/Scheduling/IScriptedPlayoutBuilder.cs
@@ -5,7 +5,7 @@ namespace ErsatzTV.Core.Interfaces.Scheduling;
 
 public interface IScriptedPlayoutBuilder
 {
-    Task<PlayoutBuildResult> Build(
+    Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
diff --git a/ErsatzTV.Core/Interfaces/Scheduling/ISequentialPlayoutBuilder.cs b/ErsatzTV.Core/Interfaces/Scheduling/ISequentialPlayoutBuilder.cs
index ff9e16a07..1d7c5645b 100644
--- a/ErsatzTV.Core/Interfaces/Scheduling/ISequentialPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Interfaces/Scheduling/ISequentialPlayoutBuilder.cs
@@ -5,7 +5,7 @@ namespace ErsatzTV.Core.Interfaces.Scheduling;
 
 public interface ISequentialPlayoutBuilder
 {
-    Task<PlayoutBuildResult> Build(
+    Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
diff --git a/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs b/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs
index bbbc9eceb..3d1ae1d2c 100644
--- a/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutBuilder.cs
@@ -27,7 +27,7 @@ public class BlockPlayoutBuilder(
 
     protected virtual ILogger Logger => logger;
 
-    public virtual async Task<PlayoutBuildResult> Build(
+    public virtual async Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
@@ -57,6 +57,11 @@ public class BlockPlayoutBuilder(
         List<EffectiveBlock> blocksToSchedule =
             EffectiveBlock.GetEffectiveBlocks(referenceData.PlayoutTemplates, start, daysToBuild);
 
+        if (blocksToSchedule.Count == 0)
+        {
+            return result;
+        }
+
         // always start at the beginning of the block
         start = blocksToSchedule.Min(b => b.Start);
 
diff --git a/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutPreviewBuilder.cs b/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutPreviewBuilder.cs
index 58715cf24..faeb9df9f 100644
--- a/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutPreviewBuilder.cs
+++ b/ErsatzTV.Core/Scheduling/BlockScheduling/BlockPlayoutPreviewBuilder.cs
@@ -26,7 +26,7 @@ public class BlockPlayoutPreviewBuilder(
 
     protected override ILogger Logger => NullLogger.Instance;
 
-    public override async Task<PlayoutBuildResult> Build(
+    public override async Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
@@ -35,11 +35,16 @@ public class BlockPlayoutPreviewBuilder(
     {
         _randomizedCollections.Add(playout.Channel.UniqueId, []);
 
-        PlayoutBuildResult result = await base.Build(start, playout, referenceData, mode, cancellationToken);
+        Either<BaseError, PlayoutBuildResult> buildResult = await base.Build(
+            start,
+            playout,
+            referenceData,
+            mode,
+            cancellationToken);
 
         _randomizedCollections.Remove(playout.Channel.UniqueId);
 
-        return result;
+        return buildResult;
     }
 
     protected override Task<int> GetDaysToBuild(CancellationToken cancellationToken) => Task.FromResult(1);
diff --git a/ErsatzTV.Core/Scheduling/PlayoutBuildException.cs b/ErsatzTV.Core/Scheduling/PlayoutBuildException.cs
deleted file mode 100644
index bd31511dc..000000000
--- a/ErsatzTV.Core/Scheduling/PlayoutBuildException.cs
+++ /dev/null
@@ -1,8 +0,0 @@
-namespace ErsatzTV.Core.Scheduling;
-
-public class PlayoutBuildException : Exception
-{
-    public PlayoutBuildException() : base() { }
-    public PlayoutBuildException(string message) : base(message) { }
-    public PlayoutBuildException(string message, Exception innerException) : base(message, innerException) { }
-}
diff --git a/ErsatzTV.Core/Scheduling/PlayoutBuilder.cs b/ErsatzTV.Core/Scheduling/PlayoutBuilder.cs
index 66af191b4..ccf9bfb68 100644
--- a/ErsatzTV.Core/Scheduling/PlayoutBuilder.cs
+++ b/ErsatzTV.Core/Scheduling/PlayoutBuilder.cs
@@ -63,15 +63,13 @@ public class PlayoutBuilder : IPlayoutBuilder
         }
     }
 
-    public async Task<PlayoutBuildResult> Build(
+    public async Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildMode mode,
         CancellationToken cancellationToken)
     {
-        PlayoutBuildResult result = PlayoutBuildResult.Empty;
-
         if (playout.ScheduleKind is not PlayoutScheduleKind.Classic)
         {
             _logger.LogWarning(
@@ -80,30 +78,39 @@ public class PlayoutBuilder : IPlayoutBuilder
                 referenceData.Channel.Number,
                 referenceData.Channel.Name);
 
-            return result;
+            return BaseError.New($"Cannot build playout type {playout.ScheduleKind} using classic playout builder.");
         }
 
-        foreach (PlayoutParameters parameters in await Validate(start, playout, referenceData, cancellationToken))
-        {
-            // for testing purposes
-            // if (mode == PlayoutBuildMode.Reset)
-            // {
-            //     return await Build(playout, mode, parameters with { Start = parameters.Start.AddDays(-2) });
-            // }
-
-            result = await Build(playout, referenceData, result, mode, parameters, cancellationToken);
-
-            result = result with
+        Either<BaseError, PlayoutParameters> validateResult = await Validate(start, referenceData, cancellationToken);
+        return await validateResult.MatchAsync(
+            async parameters =>
             {
-                RerunHistoryToRemove = _rerunHelper.GetHistoryToRemove(),
-                AddedRerunHistory = _rerunHelper.GetHistoryToAdd()
-            };
-        }
+                // for testing purposes
+                // if (mode == PlayoutBuildMode.Reset)
+                // {
+                //     return await Build(playout, mode, parameters with { Start = parameters.Start.AddDays(-2) });
+                // }
 
-        return result;
+                Either<BaseError, PlayoutBuildResult> buildResult = await Build(
+                    playout,
+                    referenceData,
+                    PlayoutBuildResult.Empty,
+                    mode,
+                    parameters,
+                    cancellationToken);
+
+                return buildResult.Match(
+                    result => result with
+                    {
+                        RerunHistoryToRemove = _rerunHelper.GetHistoryToRemove(),
+                        AddedRerunHistory = _rerunHelper.GetHistoryToAdd()
+                    },
+                    Either<BaseError, PlayoutBuildResult>.Left);
+            },
+            Either<BaseError, PlayoutBuildResult>.Left);
     }
 
-    private Task<PlayoutBuildResult> Build(
+    private Task<Either<BaseError, PlayoutBuildResult>> Build(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -117,7 +124,7 @@ public class PlayoutBuilder : IPlayoutBuilder
             _ => ContinuePlayout(playout, referenceData, result, parameters, cancellationToken)
         };
 
-    internal async Task<PlayoutBuildResult> Build(
+    internal async Task<Either<BaseError, PlayoutBuildResult>> Build(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -126,21 +133,19 @@ public class PlayoutBuilder : IPlayoutBuilder
         DateTimeOffset finish,
         CancellationToken cancellationToken)
     {
-        foreach (PlayoutParameters parameters in await Validate(start, playout, referenceData, cancellationToken))
-        {
-            result = await Build(
+        Either<BaseError, PlayoutParameters> validateResult = await Validate(start, referenceData, cancellationToken);
+        return await validateResult.MatchAsync(
+            async parameters => await Build(
                 playout,
                 referenceData,
                 result,
                 mode,
                 parameters with { Start = start, Finish = finish },
-                cancellationToken);
-        }
-
-        return result;
+                cancellationToken),
+            Either<BaseError, PlayoutBuildResult>.Left);
     }
 
-    private async Task<PlayoutBuildResult> RefreshPlayout(
+    private async Task<Either<BaseError, PlayoutBuildResult>> RefreshPlayout(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -266,7 +271,7 @@ public class PlayoutBuilder : IPlayoutBuilder
             cancellationToken);
     }
 
-    private async Task<PlayoutBuildResult> ResetPlayout(
+    private async Task<Either<BaseError, PlayoutBuildResult>> ResetPlayout(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -310,7 +315,7 @@ public class PlayoutBuilder : IPlayoutBuilder
         return result;
     }
 
-    private async Task<PlayoutBuildResult> ContinuePlayout(
+    private async Task<Either<BaseError, PlayoutBuildResult>> ContinuePlayout(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -340,9 +345,8 @@ public class PlayoutBuilder : IPlayoutBuilder
             cancellationToken);
     }
 
-    private async Task<Option<PlayoutParameters>> Validate(
+    private async Task<Either<BaseError, PlayoutParameters>> Validate(
         DateTimeOffset start,
-        Playout playout,
         PlayoutReferenceData referenceData,
         CancellationToken cancellationToken)
     {
@@ -351,7 +355,7 @@ public class PlayoutBuilder : IPlayoutBuilder
         if (collectionMediaItems.IsEmpty)
         {
             _logger.LogWarning("Playout {Playout} has no items", referenceData.Channel.Name);
-            return None;
+            return BaseError.New($"Playout {referenceData.Channel.Name} has no items");
         }
 
         Option<bool> skipMissingItems =
@@ -365,24 +369,26 @@ public class PlayoutBuilder : IPlayoutBuilder
         {
             Option<string> maybeName =
                 await _mediaCollectionRepository.GetNameFromKey(emptyCollection, cancellationToken);
-            if (maybeName.IsSome)
-            {
-                foreach (string name in maybeName)
+            return maybeName.Match(
+                name =>
                 {
                     _logger.LogError(
                         "Unable to rebuild playout; {CollectionType} {CollectionName} has no valid items!",
                         emptyCollection.CollectionType,
                         name);
-                }
-            }
-            else
-            {
-                _logger.LogError(
-                    "Unable to rebuild playout; collection {@CollectionKey} has no valid items!",
-                    emptyCollection);
-            }
 
-            return None;
+                    return BaseError.New(
+                        $"Unable to rebuild playout; {emptyCollection.CollectionType} {name} has no valid items!");
+                },
+                () =>
+                {
+                    _logger.LogError(
+                        "Unable to rebuild playout; collection {@CollectionKey} has no valid items!",
+                        emptyCollection);
+
+                    return BaseError.New(
+                        $"Unable to rebuild playout; collection {HistoryDetails.KeyForCollectionKey(emptyCollection)} has no valid items!");
+                });
         }
 
         Option<int> daysToBuild = await _configElementRepository.GetValue<int>(
@@ -397,7 +403,7 @@ public class PlayoutBuilder : IPlayoutBuilder
             collectionMediaItems);
     }
 
-    private async Task<PlayoutBuildResult> BuildPlayoutItems(
+    private async Task<Either<BaseError, PlayoutBuildResult>> BuildPlayoutItems(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
@@ -431,11 +437,11 @@ public class PlayoutBuilder : IPlayoutBuilder
         {
             if (cancellationToken.IsCancellationRequested)
             {
-                return result;
+                return BaseError.New("Playout build was canceled");
             }
 
             _logger.LogDebug("Building playout from {Start} to {Finish}", start, finish);
-            result = await BuildPlayoutItems(
+            Either<BaseError, PlayoutBuildResult> buildResult = await BuildPlayoutItems(
                 playout,
                 referenceData,
                 result,
@@ -446,6 +452,16 @@ public class PlayoutBuilder : IPlayoutBuilder
                 randomStartPoint,
                 cancellationToken);
 
+            foreach (BaseError error in buildResult.LeftToSeq())
+            {
+                return error;
+            }
+
+            foreach (PlayoutBuildResult r in buildResult.RightToSeq())
+            {
+                result = r;
+            }
+
             // only randomize once (at the start of the playout)
             randomStartPoint = false;
 
@@ -455,14 +471,14 @@ public class PlayoutBuilder : IPlayoutBuilder
 
         if (cancellationToken.IsCancellationRequested)
         {
-            return result;
+            return BaseError.New("Playout build was canceled");
         }
 
         if (start < playoutFinish)
         {
             // build one final time without continue anchors
             _logger.LogDebug("Building final playout from {Start} to {Finish}", start, playoutFinish);
-            result = await BuildPlayoutItems(
+            Either<BaseError, PlayoutBuildResult> buildResult = await BuildPlayoutItems(
                 playout,
                 referenceData,
                 result,
@@ -472,6 +488,16 @@ public class PlayoutBuilder : IPlayoutBuilder
                 false,
                 randomStartPoint,
                 cancellationToken);
+
+            foreach (BaseError error in buildResult.LeftToSeq())
+            {
+                return error;
+            }
+
+            foreach (PlayoutBuildResult r in buildResult.RightToSeq())
+            {
+                result = r;
+            }
         }
 
         if (TrimStart)
@@ -504,7 +530,7 @@ public class PlayoutBuilder : IPlayoutBuilder
         return result;
     }
 
-    private async Task<PlayoutBuildResult> BuildPlayoutItems(
+    private async Task<Either<BaseError, PlayoutBuildResult>> BuildPlayoutItems(
         Playout playout,
         PlayoutReferenceData referenceData,
         PlayoutBuildResult result,
diff --git a/ErsatzTV.Core/Scheduling/ScriptedScheduling/ScriptedPlayoutBuilder.cs b/ErsatzTV.Core/Scheduling/ScriptedScheduling/ScriptedPlayoutBuilder.cs
index 834a2abcb..7ff714f8f 100644
--- a/ErsatzTV.Core/Scheduling/ScriptedScheduling/ScriptedPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Scheduling/ScriptedScheduling/ScriptedPlayoutBuilder.cs
@@ -18,7 +18,7 @@ public class ScriptedPlayoutBuilder(
     ILogger<ScriptedPlayoutBuilder> logger)
     : IScriptedPlayoutBuilder
 {
-    public async Task<PlayoutBuildResult> Build(
+    public async Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
@@ -43,7 +43,7 @@ public class ScriptedPlayoutBuilder(
                 logger.LogError(
                     "Cannot build scripted playout; schedule file {File} does not exist",
                     scriptFile);
-                return result;
+                return BaseError.New($"Cannot build scripted playout; schedule file {scriptFile} does not exist");
             }
 
             var arguments = new List<string>
@@ -102,6 +102,8 @@ public class ScriptedPlayoutBuilder(
                     "Scripted playout process exited with code {Code}: {Error}",
                     commandResult.ExitCode,
                     commandResult.StandardError);
+                return BaseError.New(
+                    $"Scripted playout process exited with code {commandResult.ExitCode}: {commandResult.StandardError}");
             }
 
             playout.Anchor = schedulingEngine.GetAnchor();
@@ -111,12 +113,12 @@ public class ScriptedPlayoutBuilder(
         catch (OperationCanceledException)
         {
             logger.LogWarning("Scripted playout build timed out after {TimeoutSeconds} seconds", timeoutSeconds);
-            throw new TimeoutException($"Scripted playout build timed out after {timeoutSeconds} seconds");
+            return BaseError.New($"Scripted playout build timed out after {timeoutSeconds} seconds");
         }
         catch (Exception ex)
         {
             logger.LogWarning(ex, "Unexpected exception building scripted playout");
-            throw;
+            return BaseError.New($"Unexpected exception building scripted playout: {ex}");
         }
         finally
         {
diff --git a/ErsatzTV.Core/Scheduling/YamlScheduling/SequentialPlayoutBuilder.cs b/ErsatzTV.Core/Scheduling/YamlScheduling/SequentialPlayoutBuilder.cs
index 65701d8a4..adc5c0a33 100644
--- a/ErsatzTV.Core/Scheduling/YamlScheduling/SequentialPlayoutBuilder.cs
+++ b/ErsatzTV.Core/Scheduling/YamlScheduling/SequentialPlayoutBuilder.cs
@@ -26,7 +26,7 @@ public class SequentialPlayoutBuilder(
     ILogger<SequentialPlayoutBuilder> logger)
     : ISequentialPlayoutBuilder
 {
-    public async Task<PlayoutBuildResult> Build(
+    public async Task<Either<BaseError, PlayoutBuildResult>> Build(
         DateTimeOffset start,
         Playout playout,
         PlayoutReferenceData referenceData,
@@ -41,7 +41,7 @@ public class SequentialPlayoutBuilder(
         if (!localFileSystem.FileExists(playout.ScheduleFile))
         {
             logger.LogWarning("Sequential schedule file {File} does not exist; aborting.", playout.ScheduleFile);
-            throw new PlayoutBuildException($"Sequential schedule file {playout.ScheduleFile} does not exist");
+            return BaseError.New($"Sequential schedule file {playout.ScheduleFile} does not exist");
         }
 
         Option<YamlPlayoutDefinition> maybePlayoutDefinition =
@@ -49,7 +49,7 @@ public class SequentialPlayoutBuilder(
         if (maybePlayoutDefinition.IsNone)
         {
             logger.LogWarning("Sequential schedule file {File} is invalid; aborting.", playout.ScheduleFile);
-            throw new PlayoutBuildException($"Sequential schedule file {playout.ScheduleFile} is invalid");
+            return BaseError.New($"Sequential schedule file {playout.ScheduleFile} is invalid");
         }
 
         // using ValueUnsafe to avoid nesting
@@ -96,13 +96,13 @@ public class SequentialPlayoutBuilder(
                 if (maybeImportedDefinition.IsNone)
                 {
                     logger.LogWarning("YAML playout import {File} is invalid; aborting.", import);
-                    throw new PlayoutBuildException($"YAML playout import {import} is invalid");
+                    return BaseError.New($"YAML playout import {import} is invalid");
                 }
             }
             catch (Exception ex)
             {
                 logger.LogError(ex, "Unexpected exception loading YAML playout import");
-                throw new PlayoutBuildException("Unexpected exception loading YAML playout import", ex);
+                return BaseError.New($"Unexpected exception loading YAML playout import: {ex}");
             }
         }
 
@@ -236,7 +236,7 @@ public class SequentialPlayoutBuilder(
         if (DetectCycle(context.Definition))
         {
             logger.LogError("YAML sequence contains a cycle; unable to build playout");
-            throw new PlayoutBuildException("YAML sequence contains a cycle; unable to build playout");
+            return BaseError.New("YAML sequence contains a cycle; unable to build playout");
         }
 
         var flattenCount = 0;
@@ -536,7 +536,7 @@ public class SequentialPlayoutBuilder(
         catch (Exception ex)
         {
             logger.LogWarning(ex, "Error loading YAML playout definition");
-            throw;
+            return Option<YamlPlayoutDefinition>.None;
         }
     }