We have a VERY steep paved driveway, and our PM still has less than 1,000 km on it and virtually no weight in the back yet. So far, every time we go down the driveway, the left rear brake locks up when the brakes are applied. Turning off the ESC makes no difference. It's never locked up any other time. Should we give it some more time (break in), or should we have it looked at?