Sirsidoo Do you know if there was a sim or animal where you were seeing the graphics glitch? I saw something similar myself once with a no-cc sim whose outfit temporarily broke. And it's possible for the sim to be invisible if their outfit assignment broke—the body can completely disappear.
The next time this happens, pause the game, click the ground where the glitch is, select NRaas > MasterController: [with the colon, not the bullseye] Radius Purge > 3, and let me know what's on the list. (Don't actually purge anything.) If nothing turns up, increase the number. The idea is to find something in the area that's causing the glitch.
If you see a sim, you can click the ground again and select NRaas > MasterController [bullseye] > Sim > Basic > Outfit, select the sim you couldn't see before, and choose whatever outfit for them you want. If you see a small animal or an object, you can purge it; large animals can be reset.
If nothing turns up, let me know whether your computer runs Windows or macOS. For Windows, I'd like to see a dxdiag, which you can attach to a reply; if you have a Mac, please list its full specs, everything under About This Mac except for the serial number.