I got a save that has that issue.
https://drive.google.com/open?id=0B7Sa8ogmH3qhMEo2ZTBqbGprd0k
its an template issue tho im almost 100% sure it happened for me 2 or 3 times right after having used undo to remove some walls
i reported here since i figured it was a template issue.
Few other bug reports in latest build that looks related if you ask me.