Does it only affect the Bf109?
The Corsair tail dragger and Cessna nose wheel tricycle planes are not affected.
The 109 seems to change its compass heading with aircraft attitude, it looks accurate in the air but reads very low on the ground. I am unaware of this sort of effect in real life.
It makes airfield orientation difficult, the runway heading does not agree with the aircraft compass when lined up for take off.
Map runway magnetic heading.
Accurate in the air.
Way Off on the ground. The heading was adjusted very slightly in map view to exactly match the 335 magnetic aircraft and runway headings. It is not different from the 'live flight' ground view after the landing.
Hm, perhaps the maximum pivot angle of the magnetic compass is set too low. If the axis of rotation on the compass is not vertical then you can get a wrong reading (just like during acceleration and deceleration).