Re: I can't get the sensor to fit
We as the prefinal testers would regularly see amazing errors that people would do.My first new car was a 1969 Pontiac, which I kept for many years until it was destroyed by another car striking it while it was stopped. I was still driving it when the state I lived in instituted emissions tests. It failed because of excess hydrocarbon emissions. Compression test looked okay so let's look at the carburetor. Removed top cap on carburetor, then the dried-out gasket. In the top rim of the main housing was a _serious_ dent, where something pretty heavy had fallen on it, or the carb had been dropped before assembly. That carb never should have found its way into a car. The gasket had sealed the dent for many years, until it dried out. Put a little dab of gasket sealer on the dent and let it cure, then replaced only the gasket, and the car passed its emissions test well below the PPM limits for that year. I forget which company built that carb, but that wasn't the only quality problem with the car. The first month I had it a rear-window regulator let go and the glass disappeared inside the body. Then the latch that held the seat in place front-back let go. Buy American? Call me a traitor, but I don't need the drama.
Space vehicles undergo rather more stress than that carburetor, so even if a problem isn't immediately apparent, poor QA can result in catastrophe later on. As John Glenn famously noted, every part of an American space vehicle was built by the lowest bidder. The problem is, once the thing is assembled, it's impossible to know if something was damaged or mis-assembled. As someone else noted, you have to trust in the quality culture of the organizations responsible for making the beast.