Rear Suspension problems of the 2003 Mercedes Benz E500

My car (2003 mercedes E500) has had 3 of the 4 airmatic shocks fail in 50k miles. Each time, the car is not drivable and must be towed. Two of the failures occurred while driving. The front wheels cannot be turned when this occurs without damage to the fender a dangerous situation. 1 of the repairs was performed under warranty. The other two repairs cost $3000. Calls to the dealer and Mercedes Benz of north America to request a warranty repair were refused. Review of online forums for mb owners indicates many owners experience the same problem.