PreArm: AHRS: EKF3 Yaw inconsistent by

Persistent warning Arduplane 4.3.5 PreArm: AHRS: EKF3 Rotation does not match angle by XXX degrees. All with lots of >20 satellites. A new controller, the plane has not yet flown. Matek H743 controller, Matek GPS. How to fix it? What is the problem?