I checked it out a bit this morning, and it seems to be sitting completely down on the chuck, just nothing there to hold it in place. There are those little C rings but otherwise nothing that sticks out past the smooth faces of the 1/2″ drive…it just seems to be the design as far as I can tell. But I haven’t looked closely at the socket. I can do that tonight when I get home.
It has to be the C ring is collapsed or the socket is wore out. I’d say try a different socket first, Especially since that’s the one you bought used. Also, The chuck locking collar is only for a hex bit and has nothing to do with the 1/2″ square drive for a socket…Good Luck and post up what ya find out