Thanks very much for your feedback!
It's unfortunate to have to go to another shop as it's about 25 miles away. But not as unfortunate as having to return a car endlessly for little or no gain.
Do you suggest I tell the other shop about the previous attempts?
Do you know how the warranty works on these cars? To phraise that differently, I'm guessing that the shop just bills MB for any materials & labor that is warranty related. Is that accurate?
Why do you think they have been unable to make any real ground on these problems?
Again, many thanks for your feedback!