If I am understanding correctly, you can start a new game with a new Sim and you still have an invisible Sim?
Have you tried any of these tips:
1. Repair Game:
In Origin > Games Library, right-click on Sims 4 and select Repair. - It does not make any changes to the saved game files. Meaning that your saved games are safe, they won't be deleted. If you'd like you can copy the Sims 4 folder to the desktop or a USB key.
2. Turn off Origin In-Game:
Open Origin, Select Origin > Application Settings > Origin In Game tab and click the on/off switch to disable Origin In Game. - This deactivates Origin In-Game, as it has been known to cause problems with games.
3. Empty Sims personal and family inventories. Often too many items in the inventories can cause issues. - Also, having a large family and house with a lot of furniture/decor and landscaping will cause lag after awhile.
4. Reset Sim and/or Household - Have them travel
resetsim [firstname lastname]
Have them all travel to another lot, and then send them home. This should reset all family members.
-- * Use the M key for map, for fast travel.