IJadexoxoI Please make sure you're disconnected from OneDrive -- see https://forums.ea.com/kb/the-sims-helpers-blog-en/pc-managing-onedrive/12636625
Then try this:
- Drag your whole Sims 4 folder from Document > Electronic Arts to your desktop and rename it.
- Run a Game Repair in the EA App. (If you use Steam, the equivalent is Verify Integrity.)
- Launch Sims 4. You should get no list of mods on launch, and you should have no option to load a previous save. Reset your Options.
- Start with New to test if your issue recurs in a new game.
If a test save keeps working, you can start copying old files into the newly created folders.