I'm experiencing some of these same issues on a track I'm workin on and I'm not sure how, or if, its possible to overcome?....its an evening lit, outdoor track, and I feel like I'm staying minimal on the use of lighting, but I have used the small point lights along the way to highlight the rock structures....there is two areas with background scenes that are in the cameras view that could be the cause, but I dunno....I really don't experience any noticable lagging during a run, just the shadowy pixels on the right of the screen as items come into view....not sure what else to try at this point.