Happened twice now. Tight quarters backing out of 8 foot wide doorway. All the cameras and warning tones are active due to the close proximity of the car lift posts (I park under the lift) and the door jambs. I am very careful keeping an eye on the screen making sure car is centered. Out of nowhere I have experienced A sudden mechanical stop, as if I had backed into a wall or a big tree... very jarring. Only thing I can think of is it is speed related; like collision avoidance. I exit the car immediately and don't see anything at all. Your thoughts appreciated, and yes, I will have it checked out by dealer.