The Mediawiki maintenance cron job "mediawiki::maintenance::cleanup_upload_stash" attempts to "Remove old or broken uploads from temporary uploaded file storage, clean up associated database records".
While running this manually for T195392 i noticed it shows errors on commons wiki (and they could also be found in the existing error log file).
It seems to work fine on all wikis except on commons where there are some swift backend-fail-delete errors.
See `/var/log/mediawiki/cleanup_upload_stash.err` and `/var/log/mediawiki/cleanup_upload_stash.log` on `mwmaint1002`
1288 commonswiki: Getting list of files to clean up...
1289 commonswiki: Removing 4806 file(s)...
1290 commonswiki: Failed removing stashed upload with key ...