i wasn't able to resolve the problem, so i set up a new server instance and i also couldn't reproduce the error.
Still, the old instance even with actual updates is broken.
I still have no clue, BUT we changed our hypervisor from vmware to another and maybe it's related. The SID of the hdd changed as we know, some windows server machines had some weird issues... so i think maybe this change from one hypervisor to another caused the office importer fails.
But unfortunately i cannot point to the exact issue what caused this failure.
I think, this ticket can be closed.
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