Just found out you can't order a fleet from Aegean Sea to Black Sea, and now I'm going to lose the game
I've only played as in eastern power in person with a physical board, and we've always assumed it was a legal move. Today online I could have ordered my fleet in Aegean Sea to support Constantinople, but instead I decided to order it into Black Sea to cut off Russian support to Constantinople, which apparently is an illegal move. As a result I lost Constantinople and presumably the game. Fun day haha