I know the “needs three sides as lake to fill in the square” rule, but it seems like if the lake has a complete border it should still fill in, shouldn’t it? Another player in the same game had the same problem! I fixed mine by adding a lake piece inside, but that didn’t seem to work for the other guy.
Is this a bug, or works as designed? Surely the Railroad Ink makers have answered this question, but a short search didn’t turn anything up.