AFAIR, WebTools NG should have a way to trigger various tasks manually.
Backups need sufficient access permissions (i.e. “write”) to the target path that has been set under
Settings - Server - ‘Show Advanced’ - “Backup directory”
If PMS is running in a container, that can be confusing to set up and verify.
So repair didnt fix it but i know the issue. It says in logs /volume1/docker/plex/backup dont exist (it exist but i guess since /config is /volume1/docker/plex) the path should be something else. Not sure what. Let me test