I've noticed using DukeGDX that when I turn sharply (using the mouse) any vertical lines on the textures seem to bend a bit, as you'd expect with strafe tilting. I'm not sure if this is a limitation of the polymost renderer?
That's screen tearing. I guess you run an uncapped framerate and the game pushes out hundreds more frames than your monitor can handle. Try limiting the framerate to something between 60 and 144 fps and see if the warping goes away.