South San Francisco's homes carry a median build year of 1963, two years ahead of the 1965 median across the rest of the service area, so the doors here are often the first generation of steel sectional panels rather than the solid wood swing-outs you still find on older streets. That generation of door came with torsion spring hardware sized for the lighter steel skins of the early 1960s, not the insulated double-layer panels homeowners often swap in today. When someone upgrades the door but keeps the original spring and drum setup underneath, the spring is now working against more weight than it was wound for. It still turns the door, for a while, and then it doesn't. With 21,870 households in South San Francisco, the openers and springs installed when those houses first went up are reaching the end of their rated cycle count at close to the same time, which is why this area tends to produce a cluster of spring calls rather than a steady trickle.