Verify Job failing after dedupe

Hi, 

I have two Hyper-V VMs that seem to be backing up to dedupe successfully and then duplicating to tape.  I've scheduled the Verify on the dedupe job to run the following day.  This works fine for all my jobs bar 2.

They both are verifying a lot more data than has been backed up.. One show's error E000810D (V-79-57344-33037- Error- Mount failed.) the other shows E00084D4 (Unexpected end of backup set encountered on dedupe disk:5)

There's obviously something off-key with the backup so my plan was to somehow clear the historical backups and start afresh.  Question is though, how would I clear this backup from the dedupe drive.

Cheers