NVP-vProxy standalone ESXi Host whitout vCenter trouble

Standalone ESXi Host whitout vCenter

NetWorker (NVE)    9.2.1.2

vProxy                     2.1.1-41

ESXi                        6.0

I try to make a VM Image backu (NVP-vProxy). The VM has 5 virtual disks, after 1-3 disk the backup stops.

Failed to open source VMDK "[VSA_LUN01] "servername/servername_2.vmdk": VDDK Error: 18000: Cannot connect to the host.

But I can make a backup of every separate disk, without errors