I noticed this in the 3D view. Part of the floor pattern from the level above shows through the ceiling in virtual visit mode. It doesn't seem to do this in a photo created from that view, so I guess not critical, but I don't see why it's happening even so, the levels look correct: level 0: height 8', level 1: height 8', floor 1', elevation 9'.
screen grab
basic rendered photo
The room was not defined twice, I just checked. levels are 96" with 12" floor, set 108" apart. If I move the next level up to elevation 108.125" the problem goes away. I guess maybe if the ceiling had a texture, not a colour, it might not do that. seems the texture of the floor above is going all the way through the floor, not half-way as the wall textures do.
This could be also due to computing errors in the intersection between the room ceiling and the floor above. I saw a few cases where it didn't work as expected, for complex ceilings.
Could you send [url=mailto:[email protected]]me[/url] the file that caused a problem if you still have it?