I guess any project of sufficient complexity will contain unforeseen emergent situations and combinations of elements. That is certainly true of my recently produced game, Arcane Journeys the Fantasy Adventure Board Game. I have played a total of around 211 hours of this game, and refined many many things, including making a few rules changes after playing for around 100 hours. Those changes were actually some of the best in the game.
Pricing the items and their abilities needed a lot of work, since there are 120 items, and they don't all come up every game. Some items need other items to come up to work, so the combinations of those can be really rare. In fact, in all 211 hours of play, I didn't see all there was to see, which says a lot about the variety and re-playability of the game.
So now, there is an errata page for the game, to list the few things that need changing, and to post future things if they come up, but overall remarkably little needs addressing on the page.
Errata page for Arcane Journeys the Fantasy Adventure Board Game
An errata'd item. It used to say 'gain 2 gold when you enter the mountains'. Since Mountains are hard to get into, it seemed to make sense, but it turns out there are too many characters in the basic set who have an easy time entering the mountains, so it was much too powerful.