What is happening? How do I fix this???

[Kage_Kojima]

 

[fizzly]

These tiles are meant to be ceilings, not walls, so player can go on them. You need to use walls, or if you want this pattern as a wall, you need to rearrange tileset pattern a little.

 

[Andar]

If you look at the tiles in your screenshot more carefully, you'll see that every "ceiling" tile is paired with a real wall tile directly below to look like a tower.

That is part of a function to simulate a 2-level dungeon on a single 1-level map, allowing you to make a labyrinth where the player can run around the top of the walls as well as the true ground tiles, but needs an override (like a ladder-tile) to pass between the two levels.

for that to work however the ceiling tiles need to be placed above their wall tiles, they can't be used as normal wall tiles.