Henry,
If you need to clean the drives right now......
1: Stop Netbackup
2: Take a New cleaning tape
3: open the library
4: stick the tape into the tape drive
5: have a seat, an chill a second
6: tape drive will automatically eject cleaning tape when done.
7: grab tape from "cleaned" drive and repeat 1 - 7 till tape drives are clean
Don't waste your time doing anything else until you get the correct labels.
Never set Netbackup to clean the tapes drives automatically...
Why you ask?
The compound on the cleaning tapes tend to STRIP the heads of tapes drives, rendering them worthless pretty darn quick. Clean them when you feel like it, in my case 10 TB environment twice a year.
Cool?