I'd like to note that I started a new save on a separate computer (a laptop) and did not have this issue! It seems it was a problem with the latest patch not installing correctly. I completely wiped my files on this desktop computer and started from scratch, reinstalling. The issue seems mostly resolved. But I've seen hints that the shadows are still an issue.
Having this issue on ps4 . Large section of greenhouse at the back, where it connects to a floral arrangements shack, is being swallowed by the abyss... First noticed when I was adding some terrain painting to the greenhouse interior area and couldn't see to continue painting, so I tried adding some more lights, multiple of different types, including a large ceiling lamp pointing straight down as well as multiple floor lamps, nothing would dent the all consuming shadow. I gave up convinced the back of my greenhouse has a black hole inside it.
I don't know if it's related, but I have also noticed some odd interior shadow flickers happening regularly, as if the object\furniture's shadow is blinking on and off rapidly. It was large areas of various sections of house and on multiple floors. Fairly certain I never saw it happening prior to recent patches.
@Graywhispers Do you have Mods or CC? (Or did you have them in the past?) Can you add a screenshot of your blackhole in the greenhouse? Is it only when you view from certain angles? Did you try retracing the room with the wall tool to have it rebuild the ceiling and floor when completed? https://youtu.be/rx__MGVGMnc
I the last two builds that I did (since the patch right before IL) I have noticed some funky shadow stuff, but not after completing the build in both cases... it was as if some part of the build process addressed the weird shadows or areas that seemed to be leaking in light that did not normally (while building or not). The exception to this is the rounded room/porches - Those still cast an odd light, and have a matching rounded corner section/'deck' above to create their ceiling so they are 'sealed' in the only way you can with the rounded corners.
Occasionally the way a room was built causes it to not have 'sealed' all the way and the game is not seeing it as a room. In this type of case the re-tracing of the room is sometimes helpful. I also do notice some areas that flicker (tops of stair railings, sometimes seams of certain rooms, etc.). Plus there are odd gaps at the seams of some rooms from certain angles.
