Mine begin doing the same thing. It was also making a very loud noise like gears and grinding. I have taken the unit apart and determined the same answer as Jameso84. I was able to find that the belt inside the unit was simply a 3-D printer timing belt P/N 2M-136-6. This signifies that the belt is 136 mm in length, 6 mm wide, and has coggs spaced 2 mm apart. I have tried replacing the belt, and it worked for a while but began doing the same thing. I believe since it was grinding long enough, the teeth on the motor side have worn down to the point where it won’t engage the belt properly. I have now ordered the entire power brush motor assembly P/N DJ97-02486B. I have yet to receive it and install it but this should fix the problem.