I haven't had any issues with N or UHF or F or SMA connectors. It seems it's just the BNC, and it's not just the internals. I've posted on this too - there are issues cropping up where the male BNC won't fit properly into the female of another one, or the female on a piece of gear. I've tried to figure out what the issue is, but I am still not sure what they are doing wrong. It has something to do with an internal dimension, but I have no way to measure whatever it is that's out of tolerance.
Put three or four BNCs side by side if you have purchased some in the last year from different suppliers and see if you don't see different machining patterns, especially the locking notch cutouts. I see clear differences in the way the parts are made, telling me that the original specification is not being followed for some reason. Time for more pics I guess.