Potentially Dangerous Generator Failure

I had a similar experience with a coolant expansion tank for a German car. I bought a "genuine OEM" tank at a really great price. It had all the German company markings and also said it was made in China. It leaked from day one. I spent more money buying a second tank from a major retail parts outlet, and it's holding up well. It's visually identical to the defective part, same company markings and same made in China marking. I'm thinking the first part was either a counterfeit, or from a lot of defective parts discarded by the manufacturer. My point is that one was cheap and defective, the other cost more and isn't defective, and I can't tell any difference from very closely looking at them.