I dropped the car off on monday to sort out why the passenger M3 seat wouldn't release the air in the side bolster bladders. The side bolster bladders will fill, but when you try and release it, there is a click and then nothing. I had previously replaced the button since it was damaged, but that did not fix my problem, so to the shop it went.
My mechanic identified it as a failing solenoid in the lumbar valve unit (part no. 67668385631). Since there isn't a single one of these parts currently in the U.S., it'll have to be shipped in on a stock order. It's cheaper to order through ECS, so I'm doing that. In the mean time, my mechanic jerry-rigged a T-valve setup so that the side bolsters will work and I can have the car back.