So I place walls. Sometimes it lets me place the wall over the character. I can remove the wall, but still it seems as though being able to place a wall over yourself and then get stuck, interrupting your wall building activity is undesired.
I tried my best to replicate the situation in this video https://youtu.be/4SLwqYnKvy8
I was able to replicate the build over myself as it occurred previously. 2 minute video.