hey, whats up? this only happens to me? when im seeing replays, and using shift+U to see awesome views, i can see a bunch of objects and lines of the track dissappearing and appearing, why this happens?

Objects like cones, the track lines, even segments of walls, why this happens? what can I do to avoid it? please help >_<

edit: OK i just figured it out that this happens when im racing too >_<... why?! WHY!?