I've been having this problem for a few days, which makes me wonder if it's even related to the event. I put my sims on long events overnight (harvestfest or regular events), and when I go back in the morning the event says something different. I end the events, force stop the game and go back. Then there's another pink checkmark telling me an event is completed. I get credit for each event (on Llama truck). Eventually, after repeating this multiple times, my harvestfest events would come up and I could end them. Also, the goodies bags were doing strange things. Sometimes I'd open one and not get the item stated (I opened one that awarded me 25 sim cash, I watched the cash roll up, and when I left the harvestfest window it wasn't' there anymore). Sometimes I would get 2 bags instead of 1. Not sure what's going on, but I hope they fix it soon.
Edit: The event ended hours ago, but the glitch is still happening. I force stopped the game 3 separate times, each time one of my sims had a finished event. I received credit for the event each time that was not taken away. Also, I have had the "new day" login reward screen pop up a total of 3 times today.It also ended my sticker contest for the day and gave me a whole new set of stickers to give out as if it were a new day. Kind of afraid to clear the game or turn off my tablet at this point...