Game didn't detect changes in blocked build targets once unblocked

I mined out a hallway and an 8 x 8 room underground. I then build 4 wooden walls lining the inside of the cave room. Before they were built, I started moving my crafting tables into the cave against the unbuilt wooden wall blueprints. This caused the wooden wall blueprints to get a ! because they were now unreachable to  build. So I moved the now built crafting tables out of the way of the unbuilt wall blueprints. (Nothing is now blocking the unbuilt wall blueprints, not even other blueprints.) That didn't change the obstructed !. I then cancelled the unbuilt walls and then tried to completely rebuild them from scratch again now with no obstructions. The new wall blueprints again had the ! saying I cannot build because they are still obstructed. This must be a bug, unless there is some explanation I cannot think of to correct this. Awesome game in general, really loving it!

EDIT: I should add that I also had a stockpile zone in the same room. And when I saw the obstructed ! wall, if I tried to extend the zone into that adjacent square, I couldn't, but could only create a new stockpile zone there, unconnected to the rest in that square. Strange since there shouldn't be anything different about that square since there are no obstacles blocking it.