Sorry it wasn't a long term cure. Do a search on past threads as I remember people with the same issue. One in particular had it clear then come back in a few days. I'm not sure what his final cure was. It was either on this board or the "other" one. Sorry I don't have more info.
Good luck. As far as bringing it to MB stealership, I would hesitate because I had the same problem several years ago and they "replaced" the pump. Years later I find out that the same pump controls many different functions and ALL of them worked fine. My thoughts is they just reset the unit and charged for a new pump.