Sorry, no solution at all. I pimped the RAM of the Exchange Server from 8 GB to 24 GB and moved it to a faster Hypervisor. This helped a little, the error comes now only about very 10 days.
Excatly the same problem over here:
Exchange 2010 DAG - 1 active copy, 1 passive copy (2 HyperV VMs)
2 servers with CAS role - NLB (2 HyperV VMs)
The backup with GRT works fine, but restore of an email fails:
Final error: 0xe00003bf - Cann...