Generic to humanoid rotation error

I got the Ybot from mixamo (Generic rig), added a few animations to it and it works fine.
But i also want to use the kinematic function that the humanoid rig has.
So i converted the rig to humanoid via the unity inspector, and as you can guess some errors popped up.

with the the running animation for example: https://www.mixamo.com/#/?page=1&query=running+with+intention
The shoulder/upper-body moves a lot. And the butt / lower-body stays still.

But after converting to humanoid. The upper body stays still and the butt / lowerbody start to wiggle like crazy, hehe.

Is this a common problem ?
Can someone give me some pointers ?