vProxy backup fails on stand-alone ESXi server



a customer has a stand-alone ESXi server (6.5) without a vCenter. He is using NetWorker v18.1 with vProxy v2.3.0.82 to backup one VM to a Data Domain. There is only one large VM (appr. 4 TB) on the ESXi server.


Everytime after exactly 2147 GB the workflow aborts and reports:

Failed to backup virtual disk "Hard disk 1".  Failed to initialize Block Reader.  Failed to open source VMDK "[datastore1] <vm-name>/<vm-name>.vmdk": VDDK Error: 18000: Cannot connect to the host.


I searched support.emc.com and found a lot of KBs for a comparable problem ("NVP-vProxy: Failed to disable storage migration for virtual machine") but not exact this one.


Can someone give a hint ar maybe help out?