Saw this problem just now when working on a new map, tested in adv.editor and also in local play for the map in question.
Also just for testing purpose i made a new simple map with just 3 blocks, start,checkpoint and finish block. Added Fx color and Fog settings in Mediatracker>Ambiance, everything display fine at first but as soon as the End Race(outro) clip has been viewed the Ambiance settings are not displayed any more.
Hope for a quick fix
