Ghost 15 not deleting File and Folder backups to free up storage space

I'm running a Files and Folders backup, and Norton is configured to manage the space on the drive automatically ("optimize" in its terminology). However whenever the disk actually fills up with old file versions, it runs out of space and the backup fails with an error.

 

Perusing the Event Viewer reveals that Norton isn't even attempting to delete any of the recovery data to free up space.

 

What are my options?