I noticed on a build I have on going, the hearthlings chose to install the floor before they dug the required dirt out. It probably has something to do with the building being over a pre-dug cave I made several game days ago. Including screen shots. No performance issues or errors, just funky graphics
Building schematic, construction already underway.
Light colored area is the floor already installed with dirt in place, the other side is dug out
This is the cavity underneath, water is one square to each side of the cave