ZwiftHub with SRAM NX Eagle unusable?

Hey guys,
my ZwiftHub arrived on Tuesday and I am trying to get my MTB setup running.
I changed the cassette to my SRAM NX Eagle 12 speed and put my MTB on (got this cassette also out in the wild), but there is a problem:
If I tighten my thru axle, the frame of the bicycle presses against the end of the cassette (lower image), you can also see some abrasion). I cannot start cycling, the pedals wont move at any power. If I loosen the thru axle, I can move the pedals and the wheel of the ZwiftHub starts to spin.
I managed to finish the introduction workout this way, but that does not seem to be the correct way to setup and: sometimes the axle starts to tighten itself, which leads to creeping abrasion at the end of the cassette (see the upper image). On the other hand, the cassette comes loose from time to time and the chain jumps off.

Can anyone help me?

Is there a spacer under the cassette?

No, the 50T cog is mounted directly on the freehub, followed by the other cogs.
The last cog is finished by the holder with the thread to hold the casette in place (thats where the thru axle comes through)
But thats the same way it is mounted on my MTB tire