First question: do I have to first upgrade to 1.13.2 before following your instructions?
No, the point is to remove the incompatible collation, so it runs in 1.13.0
But, it may be worth updating again, now that we have a clean database.
Also, after stopping PMS, I have just run an integrity check which said “ok” without any other comment…
That is non-conclusive. Your DB may be in a weird state with half of the tables migrated to a newer revision of the DB schema. Those errors in your logs must be caused by something.
I’d recommend performing the repair procedure anyway. It can’t hurt and is a good preparation for the update to 1.13.2
While you have Plex server shut down, please erase the gracenote database files.
They are defective as well.
(Don’t worry, they will be restored automatically in the first hours after the restart.)
in the folder
/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Cache
erase these files:
gn_cachq.gdb gn_colls.gdb gn_lists.gdb