Great Canal erroneously disallows shipbuilding: screenshot available
There is a situation in the Great Canal scenario where the human player is blocked from building a ship when, according to the description, they should not be blocked.
I understand in this scenario that ship branching isn't allowed, but this has nothing to do with branching. The human player is blocked from building a ship in a straight line. I've seen it come up three times now. The erroneous shipbuilding block is enabled when an AI ship is simply in proximity.
Screenshot is available if you'd like to see the geometry where the bug arises.