Currently, the landing practice challenge on luna seems to be reproduce this bug most consistently. How to do it:
1. play the chalenge
2. Use minimal throttle if any while decending
3. Around four km at a speed of between 200 and 300 m/s the surface, vertical and lateral speed become erratic and the prograde and retrograde markers disapear from the navball, the gimbal selector on the right and the gimbals themselves.
4. At lower altitudes this stops
As can be seen in the picture, at the time of reporting this bug I am experiencing another, unrelated bug (I experienced the bug of this post a few days before this other bug occured). This bug prevents me from seeing my altitude. Because I know that my terrain loading distance is set at 4 and the bug coincided with the loading of more accurate terrain, I concluded that my altitude was around 4 km AGL. This may be inaccurate.