I notice that a lot it's like they've got bipolar lol they can get put into a bad irritated mood by other sims which i usually find is the culprit so they're angry and then go off at other sims, i think the frequency of that happening to NPCs needs to be lowered a bit cos when walking around i come across multiple sims who're angry and i'm having to make one of the first interactions i do with Sims is to 'Brighten Up Their Day' which seems to cheer them up again. But then there's a whole lot of Sims that are Bored and i have to do it for them too to be responsive to my Sims.