Yeah, apparently it can be anything from low fluid, to a bad valve body seals or the mechatronic unit itself. I've gotten quotes to change the fluid ( OEM) with filter from 570.00 to 1,000. The 570 is a mobile mechanic who used to work for BMW. But would it be worth to replace all the seals while your already in there? It seems like a alot of guess work and trial error for a vehicle at 50k miles.