A2 Tilesets keep Breaking! Please help!

[Encregen]

So I am trying to import a custom tile over top of an existing one on a copy of the ground tiles.

Spoiler: Default A2 Tileset

Spoiler: Default A2 Tileset on the MV software

I have taken this image to a photo editor and deducted from this and from research that the tiles are about 48x48 pixels. However, when I paste in my own tile into the tileset and export it out, it completely corrupts the tiles in MV.

Spoiler: A2 tileset with my custom tile replacing an existing one

Spoiler: How the custom tileset looks in MV

Could someone help me figure out what's wrong with it?

 

[Andar]

I can see several "custom" tiles that are NOT correctly formatted autotiles. Those tiles will never work correctly.

The engine creates the placement by using four quartertiles, and the autotiles are supposed to be collections of twenty quartertiles that will be used to create those tiles.

Please check this old tutorial - it is for VXA but the autotiles for MV work exactly the same:

The Official RPG Maker Blog | The Official RPG Maker Blog

The Official RPG Maker Blog

blog.rpgmakerweb.com

You just have to replace any reference to 16 pixel quarters from VXA with 24 pixel quarters for MV/MZ, but the pictures and explanations are the same. And those will show you why the custom tiles you tried to use are completely wrong.

EDIT:
And make sure the tilesheet is in the correct slot. A2-sheets can ONLY be used in the A2 slot, the other slots have different formats.