hi i'm the Phantom who explain this bug in the same forum you have seen.
the bug is really easy and you have understood well ;D
if you select a ship or a convoy while it's docked and you open the map, if you press CTRL and you right click 4 times it will appear a straight (random) line. it can be very useful if you have to circumnavigate the peninsulas.
BE CAREFUL: if you don't bring back your ship before they leave the map they will disappear (and they will never come back) and probably the game will froze (it happened to me a few times).
Some years ago i remembered that while the convoys was on the land i could send it in all directions, but now i can't do it
"they're laughing their trousers browns" can you explain me what do you mean ? my english is far away from being average