Can you try to reflash the firmware on controller with the flasher?
Already tried, no change.
Can you share a video so that we can see the mv values moving in the HW wheel calibration screen, and the sbus calibration screen for the deadband?
If you are already turn this hard, there is definitely something wrong in the wheel.
On my Herelink the range size is 620mv.
Please contact your local distributor for RMA.
In the meantime I exchanged the wheel for @MadRC 3D printed one and now I can move it approximately with a ranage size of 600mv.
However it is still a bit hard to move, because the mechanism actually touches the case if it is rotated more than the 220mv range. With the 3D printed wheel I can apply more force and the parts bend/flex a little to reach the higher ~600mv range. I don´t think this is a fault with my unit, but generally a bad design or insufficient tolerances.