I have the same problem and it says that a sim is aging up but there is no sim trying to age up. I made a lot of progress in this save and I'd hate to lose it... I reset my sim and it still didn't work.
I don't think anyone has a good solution. I have not read all of it. Someone fixed it with MCCC so if you're a mod-user and have that I guess you can try. I'd try manually aging up everyone of my sims and any other sims on the lot.. If it works you can age them down with cas.fulleditmode later :/
My dog was dying so the adoption agent came to take them away then she just left, after that my dog ran away and now it has returned I can't interact with it or feed it, ever scince the adoption agent came it said a sim in my household is dying and I cannot save the game.
