There has to be some sort of swadgine/crimping process done after the ball goes into the socket. I suspect that they did not have that process set up properly and not getting a good enough "hit" on them to make them retain properly..
But as I stated earlier in this thread, they need to run their proper set up pieces to validate their process each time that they run a batch... If not, you just end up running a bunch of junk/scrap....
It's basic manufacturing.
