@GaHedgehog There's no need to uninstall and reinstall, at least not yet. Instead, lease 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. Don't add anything to it yet; just test out a new save.
If you see the same issue, let me know whether your computer runs Windows or macOS, and if Windows, please run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
If the new save loads properly, you can transfer one of your old saves, but nothing else yet, from the old Sims 4 folder to the new one. You don't need to save your progress, so don't worry about the effects of missing mods or custom content.