The official notice
Defect
On certain vehicles, moisture could enter the driver-side door lock microswitch and cause it to corrode. As a result, the microswitch may fail to automatically engage the parking brake and/or the auto park feature when the door is opened. If this happens, the vehicle could roll away. Note: This problem could also cause the radio and/or interior lights to remain on after exiting the vehicle.
Safety Risk
A parked vehicle that rolls away could create the risk of an injury or a crash.
Remedy
To reduce the safety risk, Mercedes-Benz recommends that you should always use the parking brake when you park. Mercedes-Benz will notify owners by mail and advise you to take your vehicle to a dealership to replace the driver-side door lock.