Random outline appears in build mode

My two most recent builds (March 19, and March 20, 2025) have had strange lines or outlines appearing on the floor. The location is random, in places there was never a room, wall, or platform.

The first one is just a straight line across the floor on the first floor of a build, the second is a box shape on the second floor that extends into an open space (photo attached, area highlighted in green). 

I don't and never have had any CC in the game and don't use move objects. 

I have made 4 previous builds with Business & Hobbies before this and haven't had this issue until now.