Evault 10.4 backup is very slow after upgrading to NBU 7.5 to NBU 7.7

Evault 10.4 backup is very slow after upgrading to NBU 7.5 to NBU 7.7 

We upgraded NBU 7.5 to 7.7 after which Evault open partition backup is very slow.

previously it was working fine.now only EV backup is geting very slow

Help is appreiciated