Rayscaper only considers the material assigned to the front face and ignores the material on the back face. Incorrectly oriented faces will result in shading issues because Rayscaper uses the normal of the face to determine what's the inside/outside of an object for lighting calculations. This is no different from other rendering software.
I then attempted to reverse the faces but Sketchup froze, Rayscaper was rendering even while minimised. I checked several times to make sure I got the same thing.
What do you mean by minimized @Mike-Amos ? When the Rayscaper window is still open, even when minimized on the taskbar, it will continue rendering. You can pause the render, but if you update the geometry (e.g., when flipping a face), the geometry update needs to propagate to Rayscaper, which might be costly. You need to close the window to avoid any overhead caused by Rayscaper.
