I have just encountered the same symptoms as the OP, although mine is intermittent. Discussed with my service manager and he wants the car to pull the rear glass. My first indication of a problem was a couple months ago, when a red charging pin showed up on the nav screen for a location in which the car was never parked. I did not understand it at the time, but now it makes sense. So, if you plug in at home with the GPS stuck at some other location, you will get a new red pin on the map for where the car thinks it is. Cant help but blame the New England potholes for vibrating something loose.