Backup to local cifs mount are not deleted from /var/opt/gitlab/backups after upload


I’m running a GitLab instance, where the backups are uploaded to a CIFS mount. The local backups stored in /var/opt/gitlab/backups were uploaded to a CIFS mount and the local copy was deleted. This worked until a few weeks ago.
Now the local backups are created properly and being uploaded afterwards, but not deleted anymore.
This is my current configuration:

# Upload backups to locally mounted CIFS share
gitlab_rails['backup_upload_connection'] = {
  :provider => 'Local',
  :local_root => '/media/cifs/backup'
gitlab_rails['backup_upload_remote_directory'] = '.'
gitlab_rails['backup_keep_time'] = 259200 # 3 days

I’ve checked the logs of the backup process and found no relevant errors.

Any ideas how to fix this?