Situation: at war with pedro, conquer capitol, get a city in peace agreement, annex it, in your notification/actions queue (right side of the screen) you get a hammer/city select production notice. Immediately sell the city back to pedro for all his gpt. Bug: the select production notice stays. But you no longer own the city, so you can't select production. Nor can you right click to dismiss it (as it's a mandatory action). Nor can you just end the turn (again, it's a mandatory action). I even tried to save the game and reload... it's still there. The only way I could get around this bug was to go back to an earlier save. Solution: when you trade a city, all pending actions for that city should be cleared.