Most people call us because the door won't lift, or it lifts a few inches and stops, and the opener strains or clicks without moving anything. On a double door specifically, you'll sometimes see one side hang lower than the other before the spring goes fully. A loud bang from the garage, usually when nobody's touched the door, is the spring itself letting go - startling, but it means the fix is now, not eventually. If the door feels heavy when you lift it by hand with the opener disconnected, that's a spring already losing tension before it fully breaks.