I was playing an easy game to get some achievement, and I was shocked when totally out of the blue I got the message "foreign cultural victory imminet: Arabia only needs their culture to become dominant over one more player to achieve a cultural victory", together with "arabia has attracted enough turists to make their culture dominant over yours". I go check, and I see that arabia has 34 domestic tourists and 4 international tourists. I have 215 domestic and 152 foreign. In fact, I am trying to not win by culture as I am going for the "man on the moon" achievement. I also got a similar message in another game, except that time I was the one with little tourism and I got a notification that I was close to culture victory; another player got the culture victory maybe ten turns later. That message is clearly bugged.