Walls inside walls

[Majesty]

IDK if this has already been posted (I don't know how to search around that well), but there have been multiple times where I will have a wall, drag it someplace else, and another wall, usually lower level, is still there, in the old one's place!

 

[skylight19]

The exact same thing just happened to me...Walls disappeared after map editor, but then I realized that they were stacked on top of one another!!