I think I got a better guess and will elaborate: “cloning” hasn’t been the issue (which would be unlikely because of the sysprep also) but these machines were imported from the same HyperV-Export and thus got the same MAC-Address… will change and then try again.

I was cheering too early. Actually the MAC-Address on the Main-Network-Adapter doesn’t make a difference. So also now I’m not sure what was the diefference between this 5 and the rest when installing…

Regards