Non-Casper Issue: Time Machine Backups failing


We are looking at moving to CrashPlan (hopefully) early next year. Until then we are getting multiple TimeMachine errors like this -

"The backup disk image "Volumes/Backup6/macname.sparsebundle" is already in use. The TimeMachine host is a late-model MacMini running 10.8 Server with 8GB RAM. The Apple Support forums have not been much help and most posts state that restarting Airport Time Capsule usually resolves the issue. Nothing on OS X Server. My work around is to reboot the OS X Server and/or move user's backups to another backup drive.

Any ideas are appreciated.

Thanks! Corbin