Whats going on with this Archway placement?

I'm trying to place a few archways on this new build.. and for whatever reason it wont let me place them on these walls here. But if I build one square inward, it will. All it says is "Can't intersect with walls" uh.. What?

First picture was the build as he desired, but couldn't place archways anywhere, second one was more inward (the one you rebuilt) where he could place them. he wanted to place them in the middle, but could only place them on the very side edge in one of the rooms, not the middle.

Anyways, I have no clue what's going on, works fine for me :(