When I put a grid in my grasshopper analysis it appears in rhino as if there are coplanar surfaces there. I used a the brep input and set a rhino surface to it (layer z_grid1).
This also appears to be happening when I am using the window setup tool. It looks like there are coplanar surfaces.
see attached screen shot.
Is this something I need to be concerned about? Do I have duplicate surfaces there because I can't select them in rhino to confirm.
The culprit for me was another GH definition in that GH file so even tho I had turned off preview of the grid & windows in this "formula" I had forgotten that it was visible in the other one!