Artifacts Shader Graph vertex colors

Hey,

i am currently playing a bit with the shader graphs to get an easy and small shader for vertex color and alpha. Currently the color itself and the alpha is working. But now, with a spefici angle of the camera, i get some interesting artifacts, like the surface of this triangles are gone.

Got 2 Pcitures here, first from the artifacts and second from the little shader.

I think that i miss something.. These "blocks" are only faces.

So please xD help me out...