Broken or slipped cables
The lift cables run from the bottom bracket of the door up to a grooved drum on the spring shaft. When a cable frays, jumps its groove or snaps, that corner of the door drops and the door sits visibly skew in the opening.
A skew door binds in the tracks, and forcing it under motor power bends track sections and can pull the door off its rollers entirely. Cables are always replaced as a pair and the drums reset so both sides wind evenly — see garage door cable repair.
Damaged or misaligned tracks
Tracks take the punishment when a vehicle nudges the door, when a roller seizes and gouges the channel, or when a bracket works loose over years of vibration. Once a track is out of true, the door grinds at one point in its travel, sticks halfway, or jumps a roller out of the channel altogether.
Minor distortion can be straightened in place. Anything creased, split at a joint or bent at the radius needs the section replaced and the whole run re-shimmed — the detail is on the garage door track repair page.
Garage door opener and motor problems
Opener faults split into mechanical and electronic. Mechanically, a stripped nylon drive gear or a disengaged trolley makes the motor run happily while the door stays put. Electronically, a failed capacitor gives you a motor that hums but will not start, and a damaged control board gives intermittent behaviour that changes day to day.
In this part of Johannesburg, load shedding adds a third category. Repeated hard power cuts kill backup batteries early, corrupt stored travel limits and, over time, take out boards. If your door stopped behaving after a bout of outages, start at the battery and the board — garage door opener repair covers the full test sequence.