Things I tried before posting:
Playing a different lot with a different family (happens at the new lot too)
Clearing all the caches as described here
Uninstalling the game and reinstalling
No stilts used (didn't know that was a thing)
Windows 10
@benuathanasia Did the new lot you tested also have a platform? Platforms should work fine, as should foundations, but it's worth asking.
If this happens with items directly on the ground (or on floor tile on the ground), please switch from fullscreen to windowed mode, or vice versa, whichever you haven't been using. Quit and restart in between. And make sure you don't have any apps open that include overlays: Steam, Discord, etc. If you play through the EA App, disable its overlay too, which is under Settings > Application.
If that doesn't help either, please test in a clean folder. Move the entire Sims 3 folder out of Documents > Electronic Arts and onto your desktop, and when you launch the game, if it launches, a clean folder will spawn with no content. (Your saves and other content will be intact in the folder you moved but temporarily not read by the game.) Don't add anything to the new folder yet; just start a new save and see whether the problem is still present.
