Today, as i finished parking on a slight incline (Car facing downward, very slight incline), the car started to move forward at the Summon speed of 2 km/h indicated on the dash, however, the car was in park and no sliding occurred. This same thing happened four times as i attempted to park the car. After the fourth attempt, i had successfully parked without issue (or so i thought). I proceeded to spend the day at work and come out to find my Model S 3 meters away from where i had parked it! This is extremely irregular because The car showed itself as being in Park with the parking brake on The car moved about two meters then hit the brakes harshly while i was in it (Similar to Summon behaviour) Summon was enabled in the car, however no smartphones that could control Summon were close enough to operate the car. There are no other factors that would have come into play so far as i can think..