I might just be really dense, but I am trying to use these tiles inside of Game Maker Studio 2. For some reason the walls are (what looks like about 8px) off? Am I missing something, or am I just really stupid? Either way, help would be appreciated.
I've updated the tiles so you have a middle tile and two side tiles to the left and right. Its on version 3.2.
You should be good for now. If you don't want to use different tiles for the edges, you can always displace the floor by 8 pixels (like you mentioned), and you should get the same effect.