In the parent task it was discovered that the cleanup of old and expired backups is done before the new backups are taken.
This has several disadvantages:

• If the deletion process fails it might prevent new backups from being taken
• If the backup process fails long enough (8 days with current retention) this will delete all existing backups

ExecStart=/usr/local/sbin/wmcs-backup volumes backup-assigned-volumes
ExecStartPre=/usr/local/sbin/wmcs-backup volumes delete-expired