We have examples of this kind of thing happening[1]; in the 1970s Eli Ron invented a new way of making concrete ceilings called Pal-Kal; it was easier, faster and cheaper. Also prone to be weak if done without care and sometimes extremely dangerous. Used a lot around Israel there were some non-fatal failures and a committee setup to investigate it banned it in 1996[2]. In 2001 the Versailles Hall in Jerusalem collapsed killing 23 people. Eli Ron was given four years in prison for manslaughter. There were no good records of every building built with Pal-Kal in Jerusalem to go and check them; now any that are known to use it can be structurally checked every year, and demolished if found unsafe because there isn't a good cheap way to strengthen them, but there may be more of them unknowingly using it.
Another is the Morandi Bridge collapse in Italy in 2018[3], it had been designed as a steel cable suspension bridge with the cables encased in concrete meaning there was no good way to check if they were rusting. The engineer who designed it (click his name in Wikipedia) was calling attention to risks and problems in his design since the 1970s without the responsible companies/government departments taking it seriously enough.
Also see how big Wikipedia's "List of bridge failures" is[4]
Another is the Morandi Bridge collapse in Italy in 2018[3], it had been designed as a steel cable suspension bridge with the cables encased in concrete meaning there was no good way to check if they were rusting. The engineer who designed it (click his name in Wikipedia) was calling attention to risks and problems in his design since the 1970s without the responsible companies/government departments taking it seriously enough.
Also see how big Wikipedia's "List of bridge failures" is[4]
[1] https://en.wikipedia.org/wiki/Pal-Kal
[2] https://www.newcivilengineer.com/archive/jerusalem-collapse-...
[3] https://en.wikipedia.org/wiki/Ponte_Morandi_collapse
[4] https://en.wikipedia.org/wiki/List_of_bridge_failures