That's a track hub. see how there is a second set of stepped threads?

It looks like whoever installed that cog used a butt load of never-seize on the threads. not a bad idea, as long as you use a lockring, but I can't see why you'd use that without one on the street? The forseeable results have already happened.

My guess is this bike was set up for the track where back pressure is not an issue. Find the correct lockring, and put it on there good and tight.