Audit Library Issue

I had something crazy happen this weekend with our STK L700. It somehow ended up needing an audit of the library, but when we would run the audit it would fail. Failure of a command I can live with but there was no supporting messages to explain the cause of the failure. The library was rebooted multiple times, but the audit still was failing. Finally my resourceful manager Steve ran an audit library with the PVR and MMS flags and the audit completed successfully. The one thing it could have been was from a stuck tape in a tape drive, but why no context message to explain the failure? We had deleted the drive and the path and the tape should have been removed on the first audit since it could no longer be seen.