[OPEN] Sims excessively flirt with others (no Loyal Trait)

I'm testing this currently on a couple with no romance likes or dislikes, no romantic traits or anti romance traits, no loyal trait or romance aspirations. They're just a regular couple but they won't be having children.

I just want to test it to get the scale of the problem with the autonomous flirting and see what I can do in the game to mitigate the effects so that they can socialise with others. It's impossible. I cannot calm these two down enough to let them even have family over. I designed the lot with seating at the front of the house and a huge porch/bridge so they can chat with people without being near each other because if they've interacted or been in the house together before meeting others I can't let them chat with anyone else. They're too flirty. I had to get them to elope as I couldn't have a wedding for them. With another couple I might have risked it but this is my central family.

I sent them to a science park to collect prints from the observatory/microscope and I've had to change the lot type so that it doesn't get other visitors because they are so flirty and autonomous conversations keep popping up with random Sims. They get more and more flirty just using the park equipment without even interacting. They just have to be in the same space or have to have spoken to each other. I'm letting his conversation meter drop until he's lonely (she has the Needs No-one trait) but he's still flirty until it drops to zero and he becomes sad.

I've played this couple in my previous save games and they are part of a huge family with whom they would regularly socialise, this problem is definitely worse this year.

After exhaustive testing I've found that repeated Cold showers are not working at all, just like Unflirty isn't working and just as the romance dislikes are not working either (as I previously mentioned).

I hope this info is useful in reaching a solution for the problem.

Edit: my Unflirty Sim woke up Flirty (see attached). He also still has the Feeling Hurt by another Sim moodlet after all of the awkward conversations with his wife. Whenever she is near he gets that feeling. She constantly has to do Smooth Apology. But he has the same boosting +Flirty moodlet as his overly flirty brother in law and it may be useful in fixing the problem. They both get the Milestones moodlets when they are Flirty. So I think Growing Together may be causing it because I seem to recall that Milestones arrived with Growing Together or the associated patch. Just a thought 🤔.

After adding For Rent I've had a Sim get a Romantic Interest just walking down the street. A friend spoke to her as she was leaving the night market and before I knew it he gave her a rose from nowhere and she autonomously held his hands. Then romantic interactions popped up one after another. She wasn't in a Flirty mood. I wasn't too happy about it but her personality is super nice and friendly and I decided to add him to the game, update his look and career and get him a flat since he has a nice personality too. I just thought I give up!