The pattern we see most in Shelby: the door starts sagging on one side, or it opens partway and stalls, or it comes down faster than it should with a bang at the bottom. All three point to spring fatigue rather than the opener. On a door hung when the house was built in the late 1950s, that spring has likely never been replaced, and steel that's held tension since the Kennedy administration doesn't fail gracefully - it goes suddenly, usually on a cold morning when the metal's already stiff from overnight temperatures typical of this severe-cold part of Ohio.
A secondary symptom on these older setups is a cable that's frayed at the drum from decades of the same wrap point taking the load. If you hear a grinding or popping sound before a full failure, that's usually the warning.