Propose>Move in Glitching

I started my playable sim out in college to which she graduated. After college she begun a romantic relationship with one of her fellow college classmates. She invites him over to the lot and proposes to move in to which he ages into an adult and becomes apart of the family, but the action never fully completes as I cannot save the game and if I make them go to downtown it glitches where they both leave the lot and the lot continues to run instead of loading the community lot.

Is this a known glitch? Do I need a mod?