If you use mods or cc, try moving the whole mods folder to another place and then testing to see if the issue remains without mods/cc there.
Also repairing the game may help.
Tried moving the folder thing and repairing the game, neither worked. Others are having the same, very specific, issue [LS] LE/Reset when trying to do romantic interactions | EA Forums - 4945748
It seems the problem is if you have teens in a romantic relationship and then they age up, the glitch happens when the two young adult sims try to complete romantic socials, everything just resets. It seems like it's a glitch that started happening after the release of Lovestruck and I guess it was just never addressed by EA because they didn't think it was a big enough problem 🙄, very frustrating
