The vibrations from your garage door can cause the bolts securing the tracks to become loose.

Bent or damaged tracks can misalign the rollers and cause them to come out of the tracks.

Buildup of dirt and grime, combined with insufficient lubrication, can cause rollers to go off track.

Damage from the garage door hitting an object, or car, can cause the rollers to come off track or the door to misalign.