I changed the two drive belts on my TB30R. Now the mechanism that pushes the idler pulley of the lower belt out of the way so that the mower can be stopped and gears can be shifted will not release the tension on the belt sufficiently to allow me to stop the mower or change gears or direction of the mower. I didn't deliberately touch the linkage anywhere between the pedal and the transmission, but something changed. Any idea where I might have made my mistake?