The following error is performing a feed replication, likely due to strange/bad data. At the very least he should warn/skip the package, perhaps.

Feed replication failed: An item with the same key has already been added.
Details: System.ArgumentException: An item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) at Inedo.ProGet.Service.FeedReplicator.ReadPackageVersion(JsonTextReader reader, String group, String name, Dictionary2 packages)
at Inedo.ProGet.Service.FeedReplicator.ReadPackage(JsonTextReader reader, Dictionary`2 packages)
at Inedo.ProGet.Service.FeedReplicator.ReadPackageList(JsonTextReader reader)
at Inedo.ProGet.Service.FeedReplicator.ProcessRemoteFeedState(JsonTextReader reader, CancellationToken cancellationToken)
at Inedo.ProGet.Service.FeedReplicator.d__26.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Inedo.ProGet.Service.FeedReplicationRunner.d__3.MoveNext()