I'm having this problem now as well. I've tried all the troubleshooting solutions I've been able to find online, and it's still happening. When I load into a household, the sims will work fine for the first few seconds, they just stop doing anything and just stand there idle, both controlled and non-controlled.
Autonomy is set to High, I tried moving my households out then back in, evicted them then moved them back into the world via gallery, repaired the game, backed up files, deleted Sims 4 folder and let the game generate a new one, uninstalled and re-installed with no mods, and it's still happening. I have no idea what is causing it.