The door goes up perfectly. Coming down is the trouble: partway to the floor it stops, climbs back to the top, and the light on the opener blinks at you.
The motor runs, you can hear it working, but the door never moves. When you look up, the sprocket on top of the head is barely turning, and there is a little drift of pale plastic dust on the cover.
There is a new squeal from the front of the rail, up near the header, on every cycle. The belt has started tracking to one side and its edge is fuzzy where it has been rubbing.
You swapped the old wooden door for a heavier insulated steel one, and the twenty-year-old opener that was kept has never settled. It strains on the way up, stops partway on cold mornings, and the rail shudders with every cycle.
The small light on one of the sensors near the floor has gone dark, or it flickers when someone walks past the track. The other one glows steadily.
You bought a new remote at the hardware store, followed the little leaflet twice, and the opener light never blinked. The old remote still works.
There is a wireless symbol printed on the opener above the car, and the manual mentions an app, but the head unit has never been connected to anything. You downloaded the app once, it asked for a serial number and a network, and the moment passed.
A previous owner knotted the release cord around the rail and stacked storage shelves right beneath it. You only discovered this in the dark, with the power off, a flashlight in your teeth and a car that needed to be somewhere.