SOLVED: Strange entries in log

[TheDreadPirate]

It looks like you were deleting a collection and either the file that defined the collection wasn't present or the DB entry wasn't present. Not sure if this is a race condition or not since I don't see the logs for when the collection was original created. Only that additional movies were going to be added but were already in the collection.

I'd say it is harmless if there is noticeable issue with collections or anything else in Jellyfin.