I have a whole ton of DGX valves. They all turn smoothly for me.
As smoothly as other brands you own? What I mean is that I had thought the DGX manifold valves turned smoothly when I first got them, but when I had the opportunity to use someone else's tanks I discovered why I was having such a hard time with the valve drills. Both turned smoothly, but the Thermo turned more smoothly.
I wonder if the DGX manifold I received could have been improperly/insufficiently lubricated.