The complaint we hear most from houses in this build era is a door that groans or hangs up on the first cold morning of the week and then runs fine by afternoon. That's usually spring steel that's aged past its rated cycle count, made worse by a moderate-cold climate where the metal contracts overnight and the lift force needed to move a heavier steel door goes up right when the spring has the least give left in it. On a house built in 1981, that spring has likely had four decades of freeze-thaw cycling on it, even if it's been serviced once or twice along the way. A second common one: openers original to houses from this window are chain-drive units, and a door that reverses partway up or drifts back down after the opener stops is often a worn drive gear rather than the motor itself - a cheaper fix than owners expect, and one we'd rather diagnose in person than guess at over the phone.