It could be that it is penetrating the floor... The models do drop down from above. I'll have to try adding glide to the move commands.

Another strange thing, the white ball on the platform, it has no skin. It's just transparent, allowing you to see the image behind it. The problem is, it's becoming visible randomly. I set up a function to make one model at 0,0,0 every frame, and the ball flashes from visible to transparent. I tried setting the ball's transparency and alpha every frame, but that didn't work!