Hummm....I can not seem to replicate your bug in Chrome.
I looked into it and figured it out. It was mostly on my side. If the save game (that triggers on completing the tutorial) fails, when you enter the "real game" it spawns the tutorial box.
Probably a very niche bug, which only triggers for people who won't be able to save their game anyways.
P.S. I really enjoy these historical simulation board-gamey games.