Update to the latest firmware, 4.3.3.
Both compasses are reacting directly to the throttle output, so they are showing signs of interference. Not just the compass, but look at how the wires go to and from the compass to see if you can get those away from the power leads.
If you can do a flight for a few minutes with several 360 degree turns then you can run MagFit and get an updated COMPASS_MOT offset.