New: Monitor and Process downloads separately

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

src/NzbDrone.Core/DecisionEngine/Specifications/QueueSpecification.cs

@@ -2,6 +2,7 @@ using System.Linq;
 using NLog;
 using NzbDrone.Common.Extensions;
 using NzbDrone.Core.CustomFormats;
+using NzbDrone.Core.Download.TrackedDownloads;
 using NzbDrone.Core.IndexerSearch.Definitions;
 using NzbDrone.Core.Parser.Model;
 using NzbDrone.Core.Queue;
@@ -41,6 +42,14 @@ namespace NzbDrone.Core.DecisionEngine.Specifications
                 var remoteMovie = queueItem.RemoteMovie;
                 var qualityProfile = subject.Movie.Profile;
 
+                // To avoid a race make sure it's not FailedPending (failed awaiting removal/search).
+                // Failed items (already searching for a replacement) won't be part of the queue since
+                // it's a copy, of the tracked download, not a reference.
+                if (queueItem.TrackedDownloadState == TrackedDownloadState.FailedPending)
+                {
+                    continue;
+                }
+
                 var customFormats = _formatService.ParseCustomFormat(remoteMovie.ParsedMovieInfo);
 
                 _logger.Debug("Checking if existing release in queue meets cutoff. Queued quality is: {0} - {1}",