UPDATE: Problem solved.

I decided to tackle the issue again tonight after not getting any progress with the bike over the last couple of days. I did all sorts of tests to see why I couldn't get the cog to tighten down properly. I even did the riding up a hill and walking back down to tighten the cog and then going to town on the lockring. Nothing seemed to help. I went to far as to take video at the level of the cog and when there was slippage I couldn't see the cog move at all.

I was about to give up when I caught where the movement was coming from.....it was my f***ing chain ring bolts that were loose. It was just loose enough to slip an 1/8th of an inch in one direction or another from the center. I tightened those down and the problem was solved.