This happens some times. The LTO tape drives are designed to automatically report to the host application when cleaning is needed. The idea is that when cleaning is needed the backup will stop and request a cleaning.
1. Check Event Viewer System logs for errors from the controller driver.
2. Cleaning tapes are good for a certain number of uses.
If you don't know how many times it has been used try a different cleaning tape.
3. Check the user guide for the tape drive to see if it reports cleaning is needed via status lights or front panel. If it does that is an easy way to see if it really is an cleaning issue.
4. Check to see if it happens only with specific tapes.
5. Try a new tape of the same brand as the drive.
PM with any questions.
Nichant