I have a problem with my Sears freespirit (dyaco model909) treadmill. It has been working fine until the belt stopped in the middle of my exercise. If I leave it and try later it goes for a bit then it stops. I lubricated the belt and tried to adjust the length and it is stop and go. Can’t figure out if a sensor or board is broken. The motor is still working. I appreciate any help you can provide. Thanks, Ray.