Mine stopped after 89000 miles, The tapping it with a screwdriver didn't work for me so I took the rear parcel shelf out and took the motor of the arm and greased it and put it back together, its been fine since. I did find a BMW badge on it though.
(It is not a two minute job, if you do decide to take the parcel self out be careful not to damage the heater elements on the rear screen)