The most common version we see on these older Ashland doors is a roller popping out of the track on the bottom section, usually on the side where the cable's worn a groove into an old drum. The door will look tilted, hang crooked in the opening, or refuse to close square. Sometimes it's noisier first - a grinding or scraping sound as a roller rides the edge of the rail instead of sitting inside it.
On a lighter 1958-era steel door, a hard stop against something in the driveway or a slam from wind can knock a whole section off the rail rather than just a roller, especially if the track brackets have loosened over the decades. Because a fair number of these doors are still on their original track hardware, the metal itself can be more worn or slightly bent from age alone, which makes a minor bump more likely to derail the door than it would on a newer install.