If framerate is too low when new floor is loaded - you fall through the floor and die. I don't know what engine that is, but it has physics, which means you can perform raycasting, so you can use this to avoid situations like this by checking if there was an obstacle between point A and point B between frames. Or may be this engine has build-in feature for this, if it damages the performance, then enable it right before loading and then disable after few seconds.