The door on a house from this era usually announces trouble the same way: it starts slow on the way up, hesitates about a third of the way, then either stalls or slams the rest of the way closed on its own weight. That's a spring giving up tension, not an opener problem, even though the opener usually gets blamed first because it's the part making noise. Some owners hear a loud bang from the garage days or weeks before the door actually fails - that's the spring snapping under load while the door's sitting closed, and it means the door is now unsafe to lift by hand until the spring is replaced. If you're hearing that bang, don't test the opener on it. The cable can be under enough leftover tension to whip.