This seems like a sensor problem on the surface, but since the sensor is over 200 bucks, I'm gonna ask the experts.
Symptom: The levelling system appears to keep raising the car higher, even though the load in the trunk has not changed.
I have measured the distance from the wheel-well-edge to the tire on several occasions, and pretty much proved that'* what is happening.
My idea to prove it'* the sensor is to unbolt it from the wheel-well and rotate it to different positions and see if the levelling system reacts differently. (This method seems easier than dismantling the linkage between the sendor and the suspension piece)