Seen this posted before but no resolution. I’ve got the GPS/Mag connected to a pixhawk and when I calibrate the compass it always returns not enough data (something like that) and fails. Also, when you physically move the gps/compass unit it move on the Mission Planner monitor, but doesn’t correspond to the actual movements and usually returns back to it’s original heading even though I didn’t move it back… Strange. I saw this problem with a PX-4’s onboard compass which I didn’t resolve.
Problem solved. I dug out my last 3DR uBlox gps/mag out of my fixed wing and tried it. Calibrates fine. Just a bad compass unit.