Herelink joystick SBUS calibration issues

Hello there
I’m stuck on this problem, hoping that someone can send me in the right direction.
I cannot seem to get the configuration of the up-down movement of the right stick. It’s a selfcentered stick, but when it is in neutral, the sbus value is at max. From neutral and up, there is no change in sbus value. From neutral and down, it moves from max to minimum.
Video showing the problem: https://youtu.be/NNQ5Hyu-YbI
I cannot seem to be able to go through the calibration because of this and I cannot seem to make any adjustments in ardupilot to make up for this.
All firmware and softare is updated to the latest version.
It might be a hardware issue?
Any ideas or suggestions on how to proceed from here?

Update:
I suspected this would be a hardware problem, so I decided to investigate a little.
I swapper the two stick ‘eye balls’ - same result.
However, I was playing around with the sensor that tracks the motion of the eye balls, and if I displace it a bit from its screw holes, i can get the data on the screen to look right.
This is a bit strange and may point to a faulty magnetic sensor.