Why do certain quads of my terrain just not render?

It all started happening when I introduced roughness calculations to my material, and it hasn’t changed even if I remove them.

It goes through shader compilation, but some quads still turn out rendering with the default material as if it hasn’t compiled.
There’s nothing that differentiates these sections from others - it can happen with any combination of layers painted on it.

http://puu.sh/p7jsG/8e78f4b547.jpg

I’ve tried rebooting editor, editing material, disabling the roughness maps. Nothing seems to work, does anyone know what causes this or how to fix it?

Click on your Texture Sampler Nodes and set the Sampler Source to Shared:Wrap you can search the AH or google it it has been covered multiple times (16 Sampler limit)

I figured that’s what caused it but the material itself had only 12 samplers, so I didn’t get it.

Yeah Landscape Layer Mask are count too but they dont show up in the stats. I think there was another thing that adds to the sampler count cant recall from top of my head.