The giveaway is usually a door that looks tilted in the opening - one bottom corner sitting lower than the other, or a visible gap between the roller and the track on one side. Sometimes it's less obvious: the door runs rough, makes a grinding or popping noise partway through its cycle, or stops and reverses on its own because the opener's sensors read the resistance of a dragging roller as an obstruction. If you can see daylight between a roller and its track, or the door has stopped square in the frame, stop running the opener. Running it further usually turns a bracket job into a track or panel job, and on the newer, lighter doors common in Keller that jump happens faster than people expect.