Have you tried renaming your user folder yet ?
If not, try the following
- Close the game
- Rename Documents\Electronic Arts\The Sims 4 to Documents\Electronic Arts\The Sims 4_Old
- Repair the game
- Start the game. All your content will be gone now as the game created a new folder. All your saves/.. is still in the old folder so not to worry. Be aware that your claimed event rewards will also be gone for the time being but you will get them back with your other things.
- Start a new save game
- Check if you still have the error
- Report back with your results for further steps on how to get your stuff back.
