sproutedpup Please do a clean uninstall and reinstall of your graphics driver, as described here:
https://crinrict.com/blog/2019/02/clean-re-install-of-graphics-drivers-with-display-driver-uninstaller-ddu.html
If that doesn't help, switch from windowed to fullscreen mode, or vice versa, restarting the game before testing in the other mode.
Please also keep all other apps closed while testing. Don't open anything other than the EA App and Sims 4 once you restart after reinstalling the graphics driver, at least not until you've had a look at the game.