Happens to me too. Started after the last update. When I end a flight, the sim freezes and doesn't go to the main screen. I have to kill the sim in task manager. I have noticed though this mainly happens when I end a flight at a handcrafted airport. Anyway, I have submitted a Zendesk report and I urge you to do so too.
Edit: I even removed all my add-ons and that didn't fix it.