Worn steel rollers and hinges
That matters for how a door goes off track. Older stock tends to fail at steel rollers worn down to bare metal or hinges that have loosened over fifty years. A 2000s-era door here is more likely riding on nylon or plastic rollers in tracks that were installed once and never re-set - so off-track failures tend to come from a hard impact (a car bumper, a bike, a gust catching a door mid-cycle) rather than slow wear.
