It's really a strange thing.
Actually the support made already several remote sessions but could not resolve it yet.
We tried to disable CBT, Indexing, Guestprocessing, parallel processing... problem persists.
I turned it down that only one VM could write serial to the NAS... problem persists.
What I see is, that most jobs fail almost every time once. Some are on success state after retry 1 and some after retry 2.
But there are some VM's which are not backed up at all anymore.
Support added a registry key to the Veeam Server based on the following: https://msdn.microsoft.com/en-us/librar ... (v=sql.105
It worked once because we backed up only one disk (out of five of this VM).. but now its not working anymore neither with all disks.
While testing this I came to the conclusion that I could split up this VM to backing up only one disk per job. So I added 5 new jobs (again with parallel processing, guest processing, indexing etc enabled!) and this night they were all but one on state success!
But this is the first full backup. Now I will see in this night if the normal reverse incremental backup is working also....