How do you fix a permanent floor for a Two-Story Tall Basement Room

Question

Hi guys, I looked at the linked post that says the problem is solved, but it isn't completely:

[FIXED] Basement Split Level Rooms: Irremovable Basement Flooring | EA Forums - 11389642

First, my game doesn't have any CCs or modifications. It is updated. For the "Tag," I put "File Structure," but I don't know what that is. None of the other tags seemed to fit. I'm on a MacBook Pro M4 Pro.

The Lot is the Von Windenburg Estate, which is located on The Crumbling Isle in Windenburg. I saved the Lot on the EA Gallery. It's called "Lumon Industries Kier V.3."

I've created a structure with multiple basement levels. A couple of rooms are supposed to be two stories tall. This was working great until I added an actual two-story brick house attached to one of these rooms.

When I try to finish adding wallpaper to the outside of the upper level of this new house, a permanent basement floor is automatically created in the two-story-tall room it's attached to. Please see screenshots below.

Screenshot 1 shows the problem area. You can see a two-story house that appears to be partially inside the much larger room that is two stories tall.

Screenshot 2 is a close-up of the problem area. Please look at the one panel with brick wallpaper on the second floor of the brick house. It's on the far left.

Screenshot 3: I added brick wallpaper to the next panel to the right. This action continues to activate the permanent floor even after rebuilding part of the second story of the brick house.

Endnote: Before re-building part of the second floor, there was a lot more wallpaper. You will see this if you look at the version I saved to EA's Gallery.

Is there a solution for this?

Thank you for your help!