No idea, dude. Stress from recoil, doesn't have to be insane, just consistent. Alignment could be another big one or lose threads. I am really guessing here, I have no idea because I never used those, so I don't know.
What I have used is everything else, based on that experience, having plier handles snap, drill bit snap, tap and die kits having really bad workmanship compared to same items, but made in England, I just chose to stay clear of certain items.
Now, there's a bunch of stuff I am happy with, from China and we shop on fasttech, dx, aliexpress and many others all the time. Clothing and electronics, toys, etc. Quality is pretty good, service is excellent. However, when it comes to metal stuff, I just found it to be very bad quality and rather avoid that entirely.