New Input System - Stutter

Unity Engine
1

I have a problem that may be related to the new Input System. I have a third person character with a rigidbody controller. The controller gets turned in the direction the camera is looking at. But when testing the game in a build, the character stutters like crazy when i move the mouse. Everything is butter smooth when using the gamepad.

I am trying to fix this bug for 2 days because i really thought that i mixed Update/FixedUp anywhere and i am out of options now.
Everything is in Fixed Update.
I am using AddTorque(VelocityChange) to rotate the controller.
It is much less noticeable on higher framerates.
The stuttering is really intense when testing with Vsync locked to 30.

Is there any way to quickly use the old Input system or otherwise check if that stuttering is related to input?

Using Unity 2019.4LTS + Input System 1.1.0 preview2

2

“Is there any way to quickly use the old Input system or otherwise check if that stuttering is related to input?”

You can have both enabled at the same time if you wish. Project Settings → Player → Active Input Handling