Ok, I suspect I have the same problem as described in the thread above, only I never subscribed to the beta PMS releases 
I’m running PMS as a docker (plexinc/pms-docker:plexpass) on unRaid (6.12.15) on a ASRock Z370M-ITX/ac with 32GB RAM and a Intel Core i3-8100 CPU
The docker.img file was only 70GB (40GB in use) and for the last 4 weeks, on Friday night, the docker.img file would fill up to 100% and then goes back to normal.
As it is weekly and plex doesn’t backup it’s database anymore, I started looking into it and found this thread.
Normal backup size of the database is around 430MB. The last successful backup was on 2025-05-16 with 4820MB. The database of Plex at that moment was 58GB
I’m running the latest release (Plex 1.41.8.9834) and thus I increased my docker.img to 300 GB and started the database optimization process through the troubleshooting menu of Plex.
After reading this thread, I expected it to take a while for plex running through the database and after a while, I started to see an increase in the wal file. This increase kept going until it stopped increasing after 24 hours. the database is now 54GB and the wal file 56GB. I let my system be for an other 6 hours, but no further file edits where made so I force stopped Plex and restarted the docker.
During the optimization process, plex is unresponsive and apears to be offline. the log of unraid for the docker also does not appear to hold lots of information.
My question is the following: will plex manage to clean up the database when it will do it’s maintenance loop? And what will happen when the database cleanup is not complete when the maintenance time is up?
