It is wired as delta, what do you mean with wired correctly at the motor end? V is V, W is W, U is U.
Yes its a 2 pole motor. I checked all connections several times and do also a trough check with multimeter.
Max current is set to 8000.

I saw in different videos nobody needs torque compensation for starting motor with load.
It seams that one phase has not enough power and causes the motor stuttering under load. So I think something is wrong with my Vfd.