It's always surprising to people that a car isn't examined/tested for every conceivable set of circumstances, but the plain fact is that it would take
forever and you still wouldn't know if you got every bug out of the car. My brother worked for a dealership years ago and he said that an all new platform,
with 4 models, was delivered and come to find out, the spare tire didn't
fit. The manufacturer sent all of the shops that had the cars a tool that
they could use to alter the spare and make it fit and redesigned the spare. Whether it's my field - computer software, or a car, engineering is still engineering and the same kind of errors show up. Someone designs some part of the car (or program) and then later the parts that interface to the part are modified and no one catches the fact that the already designed part no longer works. You can count on this happening as surely as the sun rises tomorrow. The question is when does the error show up - in testing, by the dealer , or by the owner. The later it's found, the greater the cost of the error.