Thank you for your confirmation and summary.
Once "Festering Grudge Sentiment" occurs (not just for playable characters or NPCs), even if it appears to disappear over time, the characters will suddenly become mean or acquire angry moodlets. Even when having a very happy conversation, the insults will suddenly start. This has been going on for a long time and has never been resolved. Sims who experience "Festering Grudge Sentiment" always have the option to choose "Smooth Apology." (I voted for this previously.)
So I believe the cause of all of this is that "Festering Grudge Sentiment" remains in the internal data.
I sent my save data to EA a long time ago, but the issue has still not been resolved.
There's nothing that can be done about this issue on console, so I think the only options are to either reinstate the cheats or fix the bug.
I can't stand it anymore when close couples, friends, and lovers suddenly start insulting each other.