I'm opening my pool for the season (I know, it's late! ). When I turn the key to the cover, the motor turns and the cover starts to roll and then it hesitates and goes backwards, starts over, and this keeps repeating. It's like it's stuck on something. I just had the motor replaced and the cover serviced last year when I closed it. I hosed down the tracking in case there was debris, sprayed WD-40, turned the wheels a few times to make sure they were rolling ok, all to no avail. Any suggestions?