This has to be some sort of glitch, can't seem to put a wall down anywhere on this floor, yet a platform can without issues.
This isn't very consistent...
I have a boarder of platforms around a bunch of 8x8 trussing, so this floor is being supported by trussing with a platform under half of it, yet seem to be unable to stack walls ontop of the floor for some reason it seems to not be able to gain support anywhere on the floor while the platform can be placed anywhere.