I am having the exact same issue. It only happens sometimes and seems to be in the same locations every time. None of these locations are on a slope, it is level ground and when I go from park to Reverse, the car delays and then bucks really hard before moving. I have to make sure the break is held down otherwise it seems as if the car might go flying backwards. I don't know if a solution has been found for this but please let me know if you have any suggestions on what it could possibly be.