Ok, I did a quick test with no mods activated.
- First, now the sun was flat from all vantage points. I'm not sure whether I've had this problem all along. I have a faint memory of the sun halo working with some mod combination. Maybe with GWX 2.0 and OLC GUI 1.2.1, I'm not sure though. Sorry, not very helpful.

Anyway, your fix seems to almost fix it, which is certainly better than a totally flat sun.
-Secondly, I did have the hatch mod - that came with GWX 2.1 - installed. However, now that I tested the game with no mods activated, I still had the same problem with the lights. Now that I think of it, I might have had this problem from day one. So, it's most likely either a stock bug or something that came with GWX 2.x. I suspect the former.
You've really made such a good GUI that now I seem to start paying attention to little details/flaws that I might not have even noticed before.