We bought our son a used 1999 pride celebrity xl for him.to be able to ride around in the yard. Although it’s old it worked real good until late last year it started popping the overload reset button. The bearings in the rear axle were bad, I found new ones, and replace all of them. (4 or 5 of them) this year we put new batteries in it and it’s still acting the same. As soon as it gets in softer ground it loses power and ends up popping the overload. It never did this before. I removed the motor brake thinking that may have been dragging but it’s not. Motor brushes look good not that that would cause the problem. Any ideas?