So I was parked on a steep hill to give a friend a jump-start, had the parking brake and hill assist enabled, and when I was done I *thought I had turned them both off before I put the car into gear and slowly reversed down the drive way, about 15 feet. Needed to pull forward uphill a little to re-direct the car and felt stuck when I pushed the gas for a few seconds. Car didn't want to move. Turns out I did not turn off the parking brake/hill assist like I thought prior to reversing down the hill. So what did I do, grind the rear discs a little prematurely? How come the systems didn't stop me from reversing but prevented me from going forward?