Somehow Wireguard didn´t run correctly on that Backup-Machine.
So i deleted all of the config and created a whole new profile in Wireguard for that machine (but same IP)
After i established my connection SSH was working fine.... strange behaviour that only SSH was kinde screwed up but nevermind ... it works again
@JorgeB thanks for that quick reply i´ve learned again something new for future "ssh root@ip -vvv" never saw that paramenter for debugging
Edit: I´ve found the exact issue! There seems to be a dependency with my MTU Value - I set it to 1440 and the issue was reproducable - after setting it back to AUTO the issue with SSH from Unraid-Server was gone.
Hopefully this helps someone in future
