Perform the DB repair immediately after restoring a backup.
Only after that, perform the server software update, because it’s very likely that the DB adaptations in the course of the update are increasing the already-existing damage.
You might want to use GitHub - ChuckPa/PlexDBRepair: Database repair utility for Plex Media Server databases to do it.
I recommend you to read a bit about the DBREPAIR_PAGESIZE environment variable, if your plex data folder is located on a ZFS volume. PlexDBRepair development - #357 by ChuckPa
