It's astonishing that faults like this can get through.
I remember years ago learning about the way in which the Japanese car manufacturers entered the UK car market in the seventies. It was totally normal for UK built cars to suffer glaring faults like this while Japanese cars were super reliable. On a UK production line, one guy put on a few bits and the next guy put on the next bits. In Japan, one guy put on his bits and the next guy, before he put on the next bits, checked that the guy before him had done his parts correctly. So everything was double checked. That was just one of the many differences but British workers and unions didn't want to accept changes and the UK car industry died.
I assumed that today pretty much all car factories would be running in ways that would make really big mistakes impossible. I guess not, although I think they are very rare.