Hi! I searched and didn’t find my issue, which surprised me because I’ll bet others are experiencing this…
PMS running in Docker on an RPi 4, everything up to date. I find that Plex forgets items from collections. Sometimes it will forget every item that I’ve added to a collection, sometimes only a portion. The items remain in my library and I can re-add them to the collection. However some time later they may be forgotten again. Is anyone else seeing this?
I used to see users having issues if their media was on a drive that might get disconnected or take rather longer to spin-up… in combination with automatic library scans and the option for Plex to automatically empty its trash this can result in Plex dropping items from your library. If the files are picked up later, it could seem to you like they were never gone… except they lost all modifications like collection/playlist assignments.
If that could apply to your setup I recommend to disable the „automatic emptying trash“ option.
By telling us “it will forget every item that I’ve added to a collection”, do you mean that you manually added them?
If using the classic Movie agent, the collection field could be filled automatically for movies which belong to a collection in the TheMovieDB database.
I’ve seen collections there being renamed (or a name added in your language) or movies deleted from collection in a battle of moderators defending their version of what is a collection and what is not. I’ve seen this info not being available all the time during Plex metadata refreshs.
If you manually added something to the collection data field, did it lock that field? And if so, is it still locked? If not, then the whole movie “entry” is probably a completely new Plex movie object (which is tom80H aiming for) than the one you added to the collection.
Here’s one thing I noticed (which is probably an unintended bug) a while ago that might be the cause.
If you use the overflow menu to add items to a collection (… > Add to > Collection), then the collection field does not get locked. You can check by editing the item after and see that the lock on the collection field is not orange. With this knowledge, it is possible that a future metadata refresh, either manually or with the “Refresh metadata periodically”, erases the field since it isn’t locked. This is my guess but I haven’t verified it yet.
Side note, the collection field does get automatically locked if you edit the field directly from the edit window. So this method should keep the collection locked after a metadata refresh.
That sounds like the most reasonable explanation. I typically bulk add multiple items to a collection at a time. I don’t think I’ve ever seen the collection tag field get locked.
The instance of this I noticed today was in a self-created, manually populated collection of self-made videos. No online db involved.
