I can't tell you about your specific problem, but I am a firm believer in only going to a dedicated alignment shop. I have had absolutely no luck at the Benz dealer. Bought new C280-realigned at the dealer because it pulled - wore out the tires in 3000 miles-they said it was my fault, let them do it again, started wearing out a new tire in 200 miles - brought it to a real alignment shop - put 50,000 miles on the Potenzas before i needed new ones.
After that episode, I have all my cars aligned at alignment shops. And balanced. And I rotate regularly.
I'd say try a dedicated alignment shop.
Fred