why did he have to force the door up in the frist place,was it stuck or had it not being open for a long time, you need to spray wd40 oil on all moveing parts of that door, in the tracks wheels any moveing parts , blast it with spray, so the door will move with ease,then try get new cables for it , or mend the old ones, but the cables length must be set right,so the door will rise and fall without any hard work , thats why you had to cut them ,they were not set right, and its a fine art to do so, get the wd40 on it first, and take it from there,
r, March 2012