I have disabled my compass, flying exclusively in stabilize mode. I am using the Craft & Theory FrSky telemetry cable and the bad compass message repeats and is very annoying. Seems that the only way to stop it is to turn the volume off but I would like to get other alerts. This is not a pre-arm check, this is on the Mission Planner screen in big red letters for the entire flight. Is there a way to tell mission planner to ignore the disabled compass or hide the message, therefore not sending it to my transmitter?
Are you also using the C&T application? If so give the Yaapu telemetry solution a try instead. I switched to it months ago and prefer it. It shows error messages also but maybe less annoying. It’s Open Source in any case so it’s possible to modify it.
Once again calibrate the quadcopter without the external compass. I think this may solve your problem.