So your issue is that you are missing a TexCoord input for the Texture Sample that is driving the base color. You have them for your layers, but not the Base of the Blend_Overlay.
In times like this, you want to remove all the unused sections so you can simplify the issue and locate where your material is going wrong.
Texture Coordinate Node
Landscape Tiling
As you can see, when I modify the ‘Tiling’ scalar parameter value the base texture sample changes scale and the amount it tiles along the landscape.
Cheers,