Blacked out walls, floors and sims

It did happen in a new save. I found that it occurred on lots/rooms where the auto-lights feature was activated.
I turned off this feature and things went back to normal.

(I didn't have to remove any of my cc/mods.)

In my previous save, I not only turned on the auto-lights in my Sim's apartment, but also in the lobby, so that part blacked out, too. In my new save, it happened only in their bedrooms, the only rooms that were activated for auto-lights. (It was weird, because it only appeared at certain angles, and it wasn't immediate.) One of the sims only had candles in her room, the other had traditional lights as well as neon. I don't know if this was an additional factor as it has never happened before or since.

I hope this helps others going through this. I tried to post this on other threads experiencing this, but they were old posts. That made me realize this glitch has been happening for years, but I had been spared, and I have no idea why it suddenly started happening as I have always used auto-lights and i always get the same ol' cc.