PreArm: inconsistent compasses

I’m getting this error message “PreArm: inconsistent compasses” with APM planner 2 Ground station.

that message indicates your compass modules (2 onboard compasses) are reporting different values (what they shouldn’t);
1.don’t set different values for rotation in mission planner
2.currently calibration should be performed with missionplanner and onboard calibration to get right offsets for both compass modules;