This is an example of the pretty well-documented SSAO bug, that is best fixed by editing the GraphicsRules.sgr file in the same folder as the Sims4 game executable. Has been an issue for a while now, but doesn't seem to be much of a priority for the team to address (if at all). Open the .sgr file in a text editor (Notepad++ or such) and change all of the SSAOEnabled true entries to SSAOEnabled false, then save the file. You will need to do this after each update, unfortunately.