Automatic Collections Keep Popping Up Despite Turning Off In Settings

Thanks, this confirms your use of the legacy Plex Movie agent.
Unfortunately, this one won’t be getting any updates or bugfixes anymore.

All you can do is to perform these steps to try and get some old stuck configuration in the old agents “rattled free”: [HowTo] Reset metadata agent preferences to defaults and whack caches

(You might want to take a few notes or screenshots of your agent configuration before doing this.)