I personally had to fix the files-retention background job for it to work. See issue https://github.com/nextcloud/files_retention/issues/49 for details.
After that it works, but is really slow. It will run and remove files for days (we have regularly large batches of files to be removed by retention).
What I can see from the database side is that the script is removing one file at the time from the table oc_systemtag_object_mapping, and that is not efficient.
Has someone run into the same issue, and is there a reason why these rows cannot removed all at once?
I guess that the query is done by
Curious to know if others have encountered the problem.