To repair a game, go to your Origin Game Library and pick The Sims 4.
Right-click The Sims 4 icon that displays and you should see 8 options, including "Repair."
(Don't forget to delete your localthumbpackage (or whatever it's called) file and the file in your Cache-Str folder first.
Yeah, running the game continuously for awhile might be the problem.
I've actually been repairing my game before each gameplay session, whether I'm playing a Sims 4 folder with cc/mods or no.
Hope rebooting and/or repair works for you.