[OPEN] No Light/Shadow through Glass Roof

@CalyxSpaceAce  I'm the person on the same Mac who's still running Sierra, for reasons no one can quite figure out.  (What can I say, I don't like change.)  I spent a bit of time testing, and noticed a few things:

1.  Everything looks normal when a roof is not quite closed, with lighting on high or extra high:

2.  When lighting is on high (the default setting for my laptop) and both roofs cover the entire rooms, neither room is lit, and the basement loses any floor or wall texture:

3.  When lighting is on extra high, the surface-level room has proper lighting, but the basement still does not:

4:  If I place  objects in the basement (lighting extra high), those objects do have the appropriate shadows, separate from the overlay of the roof pattern:

5.  Furthermore, when I made a lot with three separate basements and nothing else (lighting on extra high), the same principles as above applied.  But when I added a small ground-level room, suddenly I could make exactly one of the three basements show correctly on command, even with a closed roof, as long as at least one of the basements was still partly open.  In this screenshot, the middle basement is open, and the other two are closed:

These screenshots are all with afternoon lighting, because the shadows stand out the most then.  The angle of morning lighting means rooms smaller than a certain size aren't lit up at all.  Lowering the pitch of the roof helps some, as does rotating the roof so that the sunlight faces a glass side.  I tried a couple different roofs, different angles, and different patterns, although not all of them, because at some point I was ready to be done; there was no difference.

So I don't know what's going on here, or why, but it's definitely weird, and it seems unlikely to be intentional.