What I would do is using compressed air clean the underside as best you can there might be a buildup of dust not allowing the yoke to extend fully, then look at the condition of the rear roller, is should have a crown in the middle, make sure the belt tracking mechanism moves freely and I believe there was a plastic cap over the screw head to push the yoke. If it is not there it might be part of your problem. Lastly make sure if you are using directional belts that they are installed correctly, You can find a breakdown for this tool at Makitatools.com