The tracks on your garage door can break for several reasons. The door may suddenly close on an object, which can cause the tracks to break, or they may become warped and fail to open and close the door properly. Broken components, such as the springs, can also cause issues with the tracks.
If you close the garage door on an object, you may also hear a loud noise with impact. Hearing a noise is also a good clue that the problem with your garage door is due to hitting an object. Even if the door doesn't come off the tracks until it hits the object, you'll want to have a technician inspect the door, as there may be something wrong with the sensors that are supposed to prevent the door from hitting anything in its path. If the sensors break, the garage door will not stop as it should when there is an object in the way.
Accidental force against the garage door can also cause it to jump off the tracks. Backing a vehicle into the garage door or hitting it with another object like a lawn mower can also damage the tracks if the door is hit hard enough.
Along with the sensors, other parts can break and force the garage door off its tracks. Broken springs, for instance, can affect the garage door's function. The door may also have trouble opening and closing properly with broken springs. Every garage door has two springs, but it's possible that only one spring breaks initially when the door comes off the tracks. Even if that is the case, a technician will likely recommend that you replace both springs at the same time. If one spring breaks due to age, the other will soon follow.