I currently am playing with a fresh 2 day old save file, and currently my sims are unable to keep friendships or romantic relationships. I was thinking it might be due to the loyalty trait when I googled any way to fix it and that showed up as a issue? But I've never had a problem with that trait before so I'm at a loss.
Is this happening just between two sims, or is it affecting many sim relationships in your game?
Try moving the whole mods folder to another place, delete the localthumbcache.package and then test to see if the issue remains without mods/cc there.
I'm currently play with two different households, and currently one of them is having a stay over and even those sims are constantly being mean to each other.
I'll move my mods folder and delete the localthumbcache.pakage and report back
