Let me first begin by saying that Watch Later is a great feature, it's just so much more convenient than any other method to Plex It videos in browsers and having them available as a list of 100 on My Queue on Apple TV later.
There is a bug, however, when one plays a video from My Queue and then goes one step back to All (the list of 100) and instead of returning to the queue, there's a grey screen with "Nothing to see here !". One then has to go all the way back to the Plex and go thru the steps again to come to reach the queue again.
Using tvOS 9.2. on ATV4 with 9.16.3 Plex on Synology 214-Play as the source.