Ideas
After installing patch 1.118, my playable Sims began to start fights autonomously, even during friendly or romantic conversations. This has never happened in my game before. All of my Sims are constantly in the grieving state due to many NPC deaths from old age (from the Life and Death expansion. They have active grief moodlets<, but those are usually overridden by positive emotions. One of the Sims is currently experiencing a Despite that, there were no active negative emotions, and the Sims were interacting normally chatting and flirting. Suddenly, one of them initiated a fight completely autonomously. This was their first fight ever< in the save. It seems that the new patch may have changed how emotional states (especially grief) affect autonomy or relationship logic. I'm playing on PC. At first, I was playing with mods (custom content only, no script mods). Later, I loaded a clean save with an empty Mods folder. There, I noticed that the Fight interaction under mean/hostile actions is now available for all Sims, not just Sims with negative friendship levels as it used to be.
Just to clarify — my female Sim has two romantic partners, and all of them have Romance Boundaries set with each other, so jealousy should not be triggered in this situation. Both partners are aware of the polyamorous relationships and usually act friendly toward each other.
However, after patch 1.118, both male Sims autonomously started fights during a romantic conversation with the female Sim. This happened twice, in different sessions, despite 100% positive relationship bars and no jealousy moodlets present.