[OPEN] Shadows on floor of second level from walls of first level

I had the same thing happen. I started deleting everything and the shadows only disappeared when I removed the staircase I had on a platform. I removed the platform and put the stairs back and no more shadow problems. There is definitely some kind of lighting bug related to stairs and platforms.

Same problem here. I had a few precisions, so I filled out the information as well. The picture files I wanted to upload are too large, but I uploaded my current problematic WiP lot to the gallery.

Product: The Sims 4
Platform: PC
Which language are you playing the game in? English
How often does the bug occur? Unsure. It seems to happen all the time with the right criteria?
What is your current game version number? 1.80.69.1030
What expansions, game packs, and stuff packs do you have installed? Everything except kits
Steps: How can we find the bug ourselves? Build a platform as the ground floor and build a staircase to the floor above to a large enough room that it encompasses some walls of the room below. A simmer on the forums helped me figure it out and made this video explaining it as well as temporary "fixes" that may work for some builds (turning walls into half-walls that are short enough or building a high-enough platform on the upper floor as well) : https://www.youtube.com/watch?v=nCbrAUgfx8g 
What happens when the bug occurs? If there are walls on the ground floor under the second-floor room that the stairs lead to, there will be shadows where the ground floor walls are. Here is a link to the lot on which I found this problem, which I uploaded to the gallery : https://ea.com/games/the-sims/the-sims-4/pc/gallery/1F17B2A81E0611EC88DD7DB6A3FFB678?category=all&searchtype=ea_origin_id&sortby=newest&time=all&searchquery=SerraNolwen&max=50&maxis=false 
What do you expect to see? No shadows from the walls of the ground floor on the second floor
Have you installed any customization with the game, e.g. Custom Content or Mods? None
Did this issue appear after a specific patch or change you made to your system? I don't know.

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? the latest as of July 28th 2022 11:00 am EST
What expansions, game packs, and stuff packs do you have installed? all except journey to batu, kids room, backyard, bowling, and toddler. I have purchased high school years but this is before the pack has gone live.
Steps: How can we find the bug ourselves? have a ladder or a lofted space then add a wall underneath the space and a light on the second floor space
What happens when the bug occurs? lighting shows a shadow of the underneath wall where the floor is flat. aka there is no wall on the second floor, but a shadow is shown like there is.
What do you expect to see? flat lighting where no random shadows occur
Have you installed any customization with the game, e.g. Custom Content or Mods? Never used.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 

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this bug also appears on the gallery when I saved the house to the gallery. I messed around a bit and the lighting issue persisted when I made the building a full second floor instead of a lofted looking space. It seems to be exaggerated when there are platforms and a part of the second floor overhangs onto the outside.  

I also have this issue.

I have built a number of rooms raised on a platform by two levels. On the floor above there are shadows that trace the walls of those rooms.