Rollers from 1979 doors
That matters here because a lot of the doors in this pocket of the service area were put up around 1979, a few years ahead of the 1983 median for the wider area we cover. Rollers on doors that age are usually the original steel wheels on worn stems, and once a roller starts binding in the track, it's rarely a one-roller problem - the whole set is usually the same age and wearing at close to the same rate.
