I think the problem is, that there are more than "some bad ones in the bunch", like maybe, most of the bunch.
They weren't carefully, and skillfully, assembled, and the receivers needed a lot more work than the "builders" were capable of.
A lot of people say, "I bought one and never had a problem",..... yet.
God Bless ya' brother, I hope you never do, but, you might yet, so stay on top of it.
Did you check the headspace?
Are you checking the ejector for mushrooming, or excessive wear?
How is the bolt contact? That's very important, so do check it out.
I'd be careful of buying those Century Galils.
Maybe only for a parts gun, or have an extremely competent Galil specialist look over it, and be prepared to have him inform you that it's receiver is not heat treated properly, and is dangerous, or some serious very serious fitment problem.