I have a 13953960SRT Craftsman 1/2 HP Garage Door Opener. The door would go down but come right back up. I tried to make limit and force adjustments. I thought I was doing okay, but while closing the door the last time....the chain slacked, the cable became extremely taught and the entire rail bowed to the left. The door is disengaged from the opener but the trolley, which is all the way to the down stop bolt will not budge. How can I loosen the tension on the cable and rail without serious damage to something or someone? The door moves freely up and down without any binding whatsoever disengaged from the opener. The manual does not cover this type of problem. Any suggestions?.