Couldn't really tell from the video.
U-joints, by their very design, accelerate and decelerate twice with each revolution when not running straight. Assuming there is nothing wrong with your locker install, this is what you are seeing.

 

I have a lockright frt locker, basically same as an aussie. The only time I notice it is when I make a slow tight turn into a parking space or some thing. How does it handle when , say turning into an itersection at some speed? Or around reg curves? If your going basically a walking speed it'll put some tension on that locker and let you know it's there when you turn.

 

I hear you... I have that same aussie installed in my YJ and by buddies TJ, they dont have the same issue with their drive shaft nor the same jerking moment.. I know the video is not the best, but between 20 and 25 seconds you can see a real pause.

I will open the diff and put the spider gears back in and see if I get the same problem. Will let you know