I know a story about a certain fighter jet we built in the United States. Programmers for the radar had everything set and they ran the tests over and over and the radar was fucking up. Don’t want to put in to many details but end result was about $100m dollars in research losses to find out the mechanic who installed the antenna on the front of the fighter turned it a quarter turn to far and it must have stripped the threads and bent the antenna slightly. Took over a month for them to catch it. They just kept assuming the programming was wrong because the antenna looked right to the eye from as close as the standard person got