@xEleanorLamb Do you get it on all lots in the gallery or only some ?
This is usually caused by mods (UI Cheat and other UI mods).
Since you say you don't have any, did you completely delete your user folder when you reinstalled ?
I thought I deleted the post, don't know why it's still up. I figured out that the problem is not that you need to delete something, you need to add something. The go to school mod bugs out the gallery and shows lots that you can't place without having the mod installed. It's quite bad. But yeah, the only solution I found so far is either to install the mod or to ignore the broken lots. The broken lots will be always there, even on a complete factory reset fresh installed game as long as you don't have the mod. It is also not all but just some lots, especially big ones usually.
I tested around a little bit. If you open the gallery in the world you wanna place the lot on, you can search the lot in the gallery, choose to place it and then choose the lot to place it on. It is showed bugged but after loading it will appear. If you are on the lot and then open the gallery to place it, it doesn't do anything.
Willow Greek High School from Romanesprt
Io Tech High School from Francoseque
Constance High School from Lukaslainelara
Basically, if you search after high school as item name and search only lots, most popular (NOT include custom content) its nearly all of the top rows.
So far I only found school related lots like that as my original post also came from wanting to place a school like building. I tried to find other lots like that with searching for apartment, villa or club but none had the same issue.
