I can't find anything online about the lag problem. My only guess is that perhaps it's because some people are playing with a capped framerate and others an uncapped one, or with vsync on or off, because when I was testing this by myself I noticed when I played with uncapped frame rate and vsync that it stuttery, though not laggy.

I'm going to rejoin a game and try that, and if that doesn't work ┐(ﾟ～ﾟ)┌