I’m Using Rover 4.0 on a Pixhawk 4.
I calibrated the compass while the Pixhawk was connected to my notebook, and it worked fine.
But as soon as I mount the compass on my rover it starts to shift, and ends up pointing in the wrong direction.
I disconnected all the devices, (RC, powerboard) and so on to make sure it does not interfere somehow.
But it still shifts, when i lift the Pixhawk 4 of my car ~1 m above the compass starts to point correctly again.