I stopped on my driveway which is at about a 20 degree angle. Placed the vehicle in park and left the engine running. I did not apply the parking brake. I exited the vehicle in order to change drivers and left the door open. The vehicle started to roll backwards slowly. I jumped in and hit the brakes. I confirmed vehicle shift selector was in park. I repeated the same thing the next day to test this but of course I stayed in the vehicle with the door shut and the same thing happened. I pulled up to the same spot, with the engine running and put the vehicle in park and I started rolling back again. I hit the brakes and it stopped. I tested this backing out of my garage and could not make this occur that way. I tried it several times again both ways and could not duplicate the problem. I know the vehicle was in park when this happened. The vehicle is brand new with less than 700 miles on it. I have stopped at that spot hundreds of times over the years with various vehicles, including other model year Jeep Grand Cherokee and this has never happened.

- Oneida, NY, USA