When I move a wall with a debug stick, parts of the wall disappear. 

What I expected to happen was...:
The missing part will appear

What actually happened was...:
A part of the wall is missing

Steps to Reproduce:
1. Place any wall.
2. Add yourself a debug stick. Change "east" to "tall", and "south" to "low".
3. If it is done right, there should be a missing part of the wall.

Note that I reproduced it some times, and sometimes it gave me unexpected results. Sometimes it worked right, and sometimes the whole wall disappeared.