HP LTO-4 drive always goes offline

Hello,

I am facing a weird issue with my backup solution which is configured as follows:

• Netbackup 7.1 installed on Windows Server 2003
• HP Storageworks 2048 with two tape drives

Now, i have always one tape drive that goes offline everytime, and logs the following Event Viewer error:

Event type :    Errorr
Source :    NetBackup AVR Daemon
Category :    Non
Event ID :    4102
Date :        18/07/2014
Time :        18:36:38
User :    N/A
Computer :    SRV-NBU-1
Description :
Fatal open error on HP.ULTRIUM4-SCSI.001 (device 1, \\.\Tape1): The specified file was not found.  DOWN'ing it

I verified the logs of the backup hardware and it shows no critical error, except standard logs that are not readable...

I don't know if this could be due to Netbackup or not,

Thanks in advance, regards!