Woohoo lowers relationship

I have this ongoing bug where sims in relationships loose relationship score once they woohoo. It's happening across several savefiles. Sims who are Soulmates can easily loose their relationship and go into the red. It doesn't seem to matter if they are spouses, romantic partners or just woohoo partners.

Currently not playing with mods, and the bug persists. I'm playing standard edition on PC, with all expansion packs, game packs and stuff packs installed.