The crazy and scary part of this scenario is if you go to the dealer and complain of a "clunking" in the rear end, they tell you thats completely normal, which it actually usually is with the last m3 and this one. But really seems tough if they are calling clunking normal when this may be and obviously was the sign of a failing part.
Not sure why they don't error on the side of fixing it and keeping a customer. They make much more than 6k off of a customer for even 1 car purchase. Sometimes the lack of business understanding is pitiful.