I bought a 500 series E-bike in February 2021 and I have 135 miles on it. Last month ( May) I went uphill and engaged the throttle and pedal assist and a grinding noise came from the hub motor, I let off the throttle and the noise stopped, for the rest of the ride everything went great. The next time I went for a ride I was going uphill and engaged the throttle and the grinding noise started again, this time I let off the throttle and rengaged the throttle and pedal assist the grinding noise started again, I let off the throttle and just started peddling the noise stopped and the rest of the ride went fine. Yesterday ( June 9) I went for a ride, started uphill engaged the throttle and pedal assist the grinding noise started and the gears would not engage, the bike stopped on the uphill road way, I got off the road and waited a few minutes, engaged the throttle and off I went like nothing happened, I rode the rest of the 15 miles and everything went fine? Thanks for reading