Parties change from Roof Raiser to Disaster at random

Hmm where you playing in a dorm or a rented lot? Girlfriend can't be asked to move in in a dorm. But anyway, I know the parties (any of them) will go from roof raising to disaster if the event the party was for did not take place. Like a birthday party, but no one aged up. Or a wedding, and nobody got married. I would assume if you through the party and your sim didn't go through the graduation scene, that would cause it. How much time was left when it tanked? Did the girlfriend move in?