Simple Material - strange translucency stencil effect in Lit mode

Blueprint novice creating my first materials.
In the attached simple Material Blueprint
My UVs all seem correct.
My Unlit mode looks fine.

But in Lit mode (middle picture below) I am getting a strange translucency or stencil effect. ie areas that should be reflective are transparent.

Can any BP experts possibly suggest what is happening? It almost seems like a render pass or depth sorting issue,