I have seen and fixed code that was first written as a prototype, then used as is in a follow on project and so on, until it turned out to be used for deciding

I have seen and fixed code that was first written as a prototype, then used as is in a follow on project and so on, until it turned out to be used for deciding on whether or not to grand certain subsidies. Except whoops in one spot it interpreted kilometers as meters without dividing by 1000. Along with literally dozens of other outright bugs. But nobody cares, really.