Shadow of a shadow?

Continuing the discussion from Shadows are not correct:

Yes, this is a known flaw in SketchUp’s handling of shadows. SketchUp’s naive algorithm assumes that “cast shadows” is turned on for everything, so shadows from a “down-sun” object overlay and hide those from an “up-sun” object. When that’s true, there is no need to deal with the problem you show. But, you have “cast shadows” turned off for the short box, and this breaks SketchUp’s logic.

my render puts yours in the shade, I think…

In your latest screen shot it is clear that your terrain drops below the ground plane. Disable Shadows on ground and you should see a change in your view. You can see the same sort of thing happening in the image below. I deliberately shifted the model down into the ground plane to create that.

Perfect! that works a treat, thanks…