build mode glitching out

@Suzicu22  Please test in a clean game folder: move your entire Sims 4 folder out of Documents\Electronic Arts and onto your desktop.  When you launch the game, a clean folder will spawn with no content.  (You can always put your old folder or its subfolders back later.)  Don't add anything to the new folder; just start a new save and play around with build mode a bit, maybe download a couple of lots from the Gallery.  Let me know whether it works, and whether you have mods or custom content.