Can't see through windows after increasing thickness to 0.25"

I’ve had trouble with Z fighting on the windows you can see in the animated GIF. So, I increased the thickness of the windows & frames to 0.25".
That created a new problem. Even though I decreased the opacity to 10%, I cannot see through the windows. How can I see through the windows and avoid Z fighting at the same time?

Can't see through windows
Complete Left Hexagon.skp (247.3 KB)

The end wall is loose geometry. There is an extra face on the back side of the window.

And there is no cut out for the window in end wall.