MissTatiBrown Please try creating a new save with no mods or custom content present, as in, move the Mods folder to the desktop and delete localthumbcache.package (again). If that works, try loading one of your saves, still with no mods or cc present. You don't need to save your progress.
If the new save works but the existing one does not, try a double load: load the affected household, receive the error, then try to load it again, without quitting or exiting to the Main Menu.
If you can't load a new save, please try a clean folder. Move the 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. (Your saves and other content will be intact in the folder you've moved but temporarily unread by the game.) Don't add anything to the new folder yet; just see whether you can start a new save.