Our backup process recently started failing with the error:
The job failed with the following error: A tape read/write error has occurred. This is usually caused by dirty read/write heads in the tape drive. Clean the tape drive, and then try the job again. If the problem persists, try a different tape. You may also need to check for problems with cables, termination, or other hardware issues.
I upgraded the tape drivers, uninstalled the drive, reinstalled it with the new drivers. I also cleaned the drive and all the other options that SYM shows on their support site.