Air shocks leaking is a common issue. Mine both went with under 45,000 miles on the clock. They start slow, and get progessively worse. Compressor will inflate them, or use height adjustment button to pump up. They will settle - sometimes takes a few days / other times happens in a few hours. I had left side go first, then a month later, right side. Go to Arnott Industries - they rebuild using BMW cores and new rubber bags. Cost $ 299.00 each with exchange which is about $ 500. less than BMW part. I was impressed by service & quality. Replacement isn't too hard - took me about an hour on first side / less on second.
Then go get your $ 1,200 back from the " faulty module " guy !