When using walls in the Crucible Editor, players can see the transparent backside of the walls unless you fill in the "roof" with tiles at a higher elevation. However, doing so will give you a "flooring not continuous" error because of the elevation. Walls seem to only count as valid edges for tiles placed at the same elevation as the wall (as in, at the base of the wall). So tiles placed at the top of the wall will not be at the same elevation as the wall, meaning the elevation difference causes the level to fail validation due to "flooring not continuous"
https://imgur.com/a/MTtEfGi

Also, the Graveyard/Stair/Edge, stair L or R 01 or 02 seem to be nonfunctional. Using normal Graveyard stairs and normal Graveyard non-stair edges will make the stair valid, but using the specific Graveyard Stair Edge tiles cause "flooring not continuous" errors at those tiles.