Check out the two videos I made about this or just read this post for the summary:
In short, there is a major bug that multiplies damage done to a wall if the wall has another wall connecting to it at an angle (on a triangle or square foundation) or if the wall has another wall right above it.
I discovered a workaround today. The bug only happens for walls. Doorways and wall frames (those wall sections with the windows) are not impacted. If you alternate walls and wall frames so that you avoid having two walls connecting on the same level at an angle, and if you avoid having two walls on top of each other, damage will work like it's intended. As far as I can tell, the windows in the wall frames don't actually work at the moment, so you won't have to worry about people shooting you at least.