Medium changer keep disappearing from Media Server

Hi All,

I am using Netbackup 7.1.0.4 Media server with AIX 6.1 recently after the Library drives upgraded to LT04 on Quantum I500 Library the medium changer is keep disappearig from Media server.

When I do a ./scan -changer it not showing anything, then again I need to go for reconfiguring it by creating the ovpass for the control path driver and it works good for few hours then again it disappear from their and the drives turns to AVR mode.

Could you please suggest what causes the problem.