When I tested folder for folder I used two households. The big one and the conspiracy guy because he has a tiny home and only has a dog. But both crashed. It even crashed when I tried to place a newly created sim into an empty lot.
I keep my mods updated as good as possible. Curseforge, sims 4 mod manager, mod hound, patreon updates... 'sigh'
After battling with copilot to actually narrow it down, because it wastes A LOT time telling me what its not, saying it can identify the file but then saying it cant... its possible I narrowed it down. But I need to wait for the save to sit for abit like a salad. Because for some reason the crashing starts the next day, not instantly.
Copilot mentioned the siminfo might be corrupt. But I found no way to access an individual sim's info in a file. S4studio cant open those files and I dont know any tool that can.