Apart from 4 leveling sensor there is another sensor for sensing the driver door close and adjust the car for last time for added driver weight. If this sensor is bad then car keeps on leveling all the time especially when u wait on red light without holding ur brakes, you can feel the dance.
Ask BMW dealer AGMC or any where you are getting your work, to check that sensor. I cant recall its exact name, im sorry.
Secondly if that sensor is fine, then you should doubt at valve body leak, pretty easy to fix (mechanic job) with few rubber O rings to seal it properly. Its near compressor. If valve body is leaking then bladder air is getting reverse to valve body and leaking from there. And when level reduce then sensor tell it to rise. Viscous circle.