I've had a strange experience in my recent game as France. I was playing for a cultural victory and doing reasonably well. Trajan and Peter were roughly ~140 points ahead of my tourism output when I started being serious about it. I was narrowing it down slowly, checking every couple of turns how fast I was closing the gap. So at one point I open the culture victory panel and notice that somehow suddenly I needed 260 foreign tourists to win when it had been only 230 foreign tourists like 3 turns earlier. I wondered how Trajan or Peter had accomplished that feat, but on closer inspection I realized that Korea had jumped from ~160 to ~260 domestic tourists within just a few turns (maybe 3-5 turns or something like that). How is that possible? Is it a bug? Has anyone experienced this before? Because playing culture games is entirely pointless until I figure out how such a thing can happen and what I can do about it.