How to find broken mods in The Sims 4

1. Close the game. Open Documents > Electronic Arts > The Sims 4.
2. Move the Mods folder to your desktop. Also delete localthumbcache.package so old mod data is cleared.
3. Start the game and test. If the problem is gone, a mod or CC file caused it.
4. Move half of your mods back into the new Mods folder and test again.
5. If the problem comes back, the broken file is in that half. Split that half again and test.
6. If the problem does not come back, those mods are fine. Add half of the rest and test.
7. Repeat until one mod is left. Remove it, or get an updated version from its creator.

When the game hits an error it can't handle, it writes a lastException file (or lastUIException) to Documents > Electronic Arts > The Sims 4. Open it in any text editor and look for mod names.

Better Exceptions, a free script mod by TwistedMexi, reads these errors for you and opens a report that names the likely file. You can also paste the file into our LastException reader.

The game makes its own Resource.cfg file in the Mods folder. Leave it there. If you move the Mods folder out and start the game, it makes a new Mods folder with a fresh Resource.cfg.

Mod .cfg files are different: they hold that mod's settings, so deleting one resets that mod.

Game updates turn mods off, and old mods can break. Start the game with mods off and check it works. Exit without saving: if you Save and Exit before you turn mods back on, CC may be removed from your save.

Check each creator's site for a version that works with the new patch. Then go to Game Options > Other, tick Enable Custom Content and Mods (and Script Mods Allowed for script mods), and restart the game.