Cables connect to the Bottom Fixture and the Drum. These are set after the door has been leveled to insure that the door rolls smoothly. Sometimes the cable will come off the drum. This happens often if a torsion spring breaks or if an object is interfering with the door going up or down.
Sometimes we have found that the cable will spin off the drum if the door has been installed incorrectly -usually the culprit is a garage door that has been installed without being leveled. The door must be level when the concrete is off level otherwise the door will not operate smoothly and you will have continual problems. Such as the cables spining of the drum.