Zenon problems

Hi i was womdering if any one could shed some light on my problem with the leveling system on my e46 m3.

Over the past week my lights have started the habit of dropping themselves to the lowest level giving me terrible vision at night. i have checked the zenons move when the car starts up which they do nice and freely, and i have also checked the metal adjuster bar and the little black box which are connected to the bottom arm on the drivers side and these parts work perfectlly, I unbolted the metal aduster arm and moved the black plastic arm which pivots on the black box and this moves the zenons up and down as it should. but still when i start the car up and switch the lights on the lighting level is fine then after a certain amount of time 5 min+ or if i switch the lights off and on again in the same day the zenons are facing the floor.

They seen to be fine first thing in the morning after a long rest period ie over night, Maybe reseting themselves I dont know? Any help would be very thankfull.

  Cliff