Limited time event 'regressed'. Has anyone else had this issue

With the new limited time event, I passed part 1 and 2 (and have the confirmation on the to do tab). 
I got a notification to upgrade grilled cheese to another level then the app crashed and i'm back to the second part (use color boosts 4 times). I've restarted the application but nothing changes. 
Has anyone else had this problem / found a solution ?