However, there have been numerous reports of Glock replacing extractors, ejectors, RSAs, and individuals doing the same, all to no avail. One company experimented with all of that in an attempt to isolate the problem. He basically did what was described in the thread link you posted. His conclusion? None of that helped. What did help was lowering the ejection port. But again, I think that fixed that gun. The frustrating thing is, will that fix the next 100 guns?
I'm an engineer, and a pretty decent machinist as well. It is extremely, extremely difficult for me to believe that a Glock is so precision manufactured, that one part, especially an extractor, being of by one thousandth of an inch, would stop a Glock from working. For reference a human hair is about 3 thousands of an inch.
But that's kinda what this thread is about - we didn't see these kinds of things in older Glocks. We basically bought them, shot them, knowing they'd work right every time.
It's just disappointing to hear the gun company that represents uber reliability seems to have lost it's way lately.