After building a hollow stone wall out of slabs and then completing a standalone wall with a door to cap it I assigned two more standalone walls to be built, each with a door in it. the first one was fine, but the second one, when I went to place the door, threw up this error:
I managed to undo most of it except for the rather stubborn wall part. The wood pillars obeyed and went away.
I’ve yet to get any of my stone walls built with a door or window. I’ve just given up trying.
My work-around for my exterior wall, is to build a small house with the door facing out of camp. Blow the back wall and roof off and build camp walls right up to what’s left (bed optional, heh):
I’d leave the roof, but it hangs down one block past the top of the walls and you can’t close that gap.