What would cause a garage door to come off track?

A garage door can come off track due to several mechanical failures, impacts, and wear issues that cause rollers to leave vertical and horizontal tracks. The most common cause is hit by car, as even low-speed bump can bend tracks and force rollers out, causing door to be crooked and jammed. Broken or weak springs cause loss of tension that keeps cables taut; when spring breaks, cables go slack and door becomes heavy and uneven, causing rollers to derail. Broken or frayed cables that snap or come off drums cause one side of door to drop and rollers to leave track. Worn or damaged rollers that are cracked, rusted, or missing ball bearings bind in tracks and can pop out, especially if tracks are dirty or dented. Tracks themselves can be bent from impact, loose bolts, or improper installation where vertical tracks not plumb, causing rollers to not seat. Loose or missing track bolts cause tracks to spread apart and rollers to fall out. Operating door manually too quickly or unevenly after pulling emergency release can cause cable slack and derailment. Attempting to close door with obstruction underneath causes door to push and go off track. Lack of maintenance like not lubricating rollers and not keeping gutters clean causing water damage and rust that weakens tracks contributes. To prevent, avoid hitting door, maintain springs, lubricate rollers, and have annual professional inspection.