Hello old thread, I believe I have found the solution to this issue, or at least one major solution to one major way in which this red sky phenomenon manifests. There may be multiple ways it can occur, but hopefully my findings can help others as well. For a tl:dr skip to last paragraph, but I will describe my full experience for the sake of science.
Up until this past week, I can only remember encountering this "red sky" glitch very rarely, with the exception that I think I saw it at least twice on Old Head, but now I encountered the issue highly consistently on my own course Im working on, I think it appeared nearly every single time I got to two certain holes in my practice "rounds" (I wasnt playing, just checking stuff). I had just made my early drafts of a panorama for the course, so I felt pretty strongly it was an issue relating to the panorama, particularly since I believe I remember something like that, with low horizon lines, being brought up in this thread at some point. That did not turn out to be the case.
I tested a lot of things back and forth, I first thought my panorama was just too low in its lowest places, but changing that didnt help, even swapping to another pano known to be fine didnt help! I tested lots of other stuff including pulling the whole plot up and down and around and nothing seemed to fix it, I was actually beginning to worry I might never figure it out and might have to accept the problem on my course... Thankfully, it was really convenient and quick to test out new things I could think of, since, if I opened the course in practice mode, and only had certain tee shots rendered in a certain sequence, the red sky would always show up at one particular hole in the exact same spot. Strangely enough opening that hole to begin with didnt produce the red sky problem at all on that hole, but still seemed to come around on some other random hole if I kept selecting other practice holes. This suggests that during normal play, it wont appear consistently at the same times or places, though some spots may be more likely than others.
Finally something I tried changed something, swapping my reflective water to some other texture changed the exact area of the red sky, but still on the same hole. However removing all water from the whole course did not solve the overall problem... Mysterious as that was, it made me wonder if it had anything to do with textures, and so I tried changing all textures on my whole course into a stock green texture (except for tee areas which I changed into stock tee texture, since tees arent allowed to be planted on anything other than a fairway category texture). This removed the red sky suddenly. After that it was fairly quick to track it down to the offending texture, which turned out to be two different stock ones that I was using as temporary placeholders for areas I had not finished creating. I tested a bit more and found that the red sky could turn up even if the offending texture only existed in some small corner of the plot, even if not being within render view when the red sky first appears.
In conclusion:
Courses having either of the following stock textures: Concrete and Asphalt (both near the top in the texture list) seem to fairly consistently cause the "red sky" issue at seemingly random times and places of the course. I highly advise designers to not use these textures. I dont know if only certain users/systems will have the issue, but clearly it is at least a decent amount of people experiencing it, and I believe I am correct in saying that Old Head suffers from the same issue that my course was. Possibly there are other stock textures causing it as well, but the standard ones such as green, tee etc dont seem to do it. If encountering the issue with high frequency on any course I recommend taking a look at which stock textures exist on the course, and to test replacing them. I might need a little more testing to say for sure my issue is completely gone, but so far it very much seems to be
