Adaptive headlights prone to misalignment?

[Da Hapa]

My search found several good threads, including a great "how to align your headlights" thread, but none specific to my question.
My '08 E90 M3 has adaptive headlamps. When I bought the car earlier this year it had 43,000 on the odo but the headlights were poorly aligned. The selling dealer fixed the alignment no questions asked but now, about 8 months and 5,000 miles later the lights are mysteriously all out of whack again. The car hasn't had an accident or ran any particularly rough roads.
I can realign the lights again but want to know if this is common (a buddy had an E46 M3 that had a passenger side xenon light which would consistently just point at the ground and the dealer replaced or fixed the assembly several times before he sold the car) or if there might be a failed part I need to investigate.
Thanks in advance.