Landmarks always have to be in the same position relative to the rest of the area the level change is in. You can move the geometry around, but you have to move the landmark with it. Otherwise, the best case scenario is that the level change isn't seamless. The player could get stuck in a wall, the void, etc, if this isn't the case. I could be wrong, but I think this is the cause of the player dying on level change.
Also, make sure the landmarks have the exact same name if they don't already.