[HSY] Duplicate Valedictorian Sim

1. In my existing save, the Go to Event button of Graduation on the calendar on Sunday 6.00-11.30pm is not grey out in the existing save file even it was not Sunday. It happened even on Friday. So if I go to the event before time, the Auditorium will be normal setting, not the Graduation one. There will be a pop-up nearby the phone icon to Go to Event at Sunday 6pm anyway as expected. 
2. In my new save without mod, the Go to Event button is grey out when it's not the time of event which I think it was supposed to be. (see screenshot)
3. In my existing save, when I performed interaction with other sim to Ask about Graduation, they will pop-up a notification says that my sim graduated normally and there's nothing to prepare despite there is Practice Valedictorian Speech on the mirror object. 
4. In my new save even without mods, when I performed interaction with other sim to Ask about Graduation, they will pop-up two notifications (see one of the screenshots) says that my sim graduated as Valedictorian and then my sim graduated normally. So I think the glitch starts here. 
5. In both save even without mods, my Sim can Practice Valedictorian Speech at the mirror. Once I finished the interaction, there will be a pop-up "Wow! What a speech..." (see screenshot). From the dialogue, it sounds like it should occur when my sim gave a speech at the event, not the practice. If I command to practice again at the same interaction, it will be immediately finished and the same pop-up appears.
6. In my existing save, at the Graduation event, there will be another Valedictorian sim who is an unplayed sim give the speech meanwhile my sim was marked as Graduate role in the event, not the Valedictorian. I can't interact with podium to give speech at all.
7. I replayed the same save file, I tried manipulating by making my Sim performed an interaction Practice Valedictorian Speech at the mirror, once I performed, the interaction was immediately finished with a pop-up "Wow! What a speech..." (see screenshot). As a result, all Sims on the lot will sit at the event including my Sim, performing interaction Listening to the speech while there was no one at the podium until it finished. 

I haven't reached to the Graduation day in my new save file yet since it will take time. However, these are the differences I found so far and again, I think it caused by there's another Valedictorian Sim from my played household who grew up around the same week as my active household.