Thanks for the reply.
The pulley (balancing wheel) looks OK, but is slightly rotating "offcenter" as you can see on the youtube above.
If the center bolt would have been rotating without any uncircular movement, I would suspect the pulley or the hub that the pulley is mounted to with the six bolts.

But now all of it moves unconcentric when the enginge is running. I can not figure out anything else than that the center bolt is deformed.

It's like if you put a drill in a drilling machine, a straight drill will rotate like a line however you move the drilling machine. If you put a bent drill in the machine, it will wobble.

The car is back at the dealer today. I've paid approx EUR1500 for this and I would really like it to be as good as it was before the chain change...