This is using HP DAT 160 external USB tape drive. The backup software is HP Backup Protector Express 3.50 SP2. There are Daily backup and Weekly backup schedules. Daily backup is differential while weekly backup is full backup.
The problem is daily backup is working fine. While weekly backup mostly end up failed with the error message as shown:
Error 1040: No device specified or all devices are now offline
What is the root cause?