Sims 3 Graduation lacking the added trait

I recently re-downloaded the whole game so I doubt it has to do with a corrupt file. This is the 5th time this has happened where my sim does not get the added trait after graduation. Only two out of many sims got it. Is it a bug that they need to fix or has anyone figured out how to fix this in their game? I saved before the ceremony and am still trying to get her that added trait. I have tried 3 times so far. I think the way I will avoid this problem in the future is to not invite friends to the graduation. They block the path to get there on time. I already stopped bringing more than one Sim to the University at a time the first time this happened. I will try one more trick and see if I can teleport her to the door before the ceremony ends. If that doesn't work I give up on that one. I just need to know if I am the only one who has had this problem or if it is quite common?