Tried the different versions these days and today with v. 20241228 aka 5.0.2 it worked.
At first the job aborted and the error log showed error 0x80042306 again.
As this is a common error with VSS backups I went through a list of suggestions from the net. What made it work on this server was to re-configure VSS on the volume via explorer context menu. On/Off, change size, finally let it at unlimited for the system volume (has 8 shares).
Might have been leftovers from a previous installed acronis server edition. It uninstalled clean, but has been using VSS.
At first the job aborted and the error log showed error 0x80042306 again.
As this is a common error with VSS backups I went through a list of suggestions from the net. What made it work on this server was to re-configure VSS on the volume via explorer context menu. On/Off, change size, finally let it at unlimited for the system volume (has 8 shares).
Might have been leftovers from a previous installed acronis server edition. It uninstalled clean, but has been using VSS.