Citicorp Center engineering crisis
In July 1978, a possible structural flaw was discovered in Citicorp Center (now Citigroup Center), a skyscraper that had recently been completed in New York City. After investigations from a number of third parties, the building was found to be in danger of possible collapse due to its design; workers surreptitiously made repairs over the next few months, avoiding disaster.
Source: Wikipedia — Citicorp Center engineering crisis (CC BY-SA 4.0)