Achievements reset

I have a save file where I use no mods and no cheats. I also clear my caches before I load this game. I play in multiple households for the 10 households for 10 generation achievement. I also have one sim that is the main focus because it's a super sim challenge. The super sim is in the university stage and she always moves out to a new household to stay in the dorms during her terms. Once the term is over, I move her back into her original household as that is the household that I'm keeping all of the unlocks for such as CAS and build/buy unlocks. The main household never gets deleted because I always leave the Super Sim's other family members there. Today, I loaded the game with the university household that holds the Super Sim and I noticed I immediately got 3 achievements that I had previously unlocked. I checked the achievement screen and these 3 were the only ones unlocked despite having over 2,000 points before. I quit without saving. When I reloaded the game, I loaded back into the main household instead of the university household first. I noticed my 2,000 achievement points were there again.