I had a similar situation with the Gunboat. I got a message that Japan had invaded New Guinea. I happen to be in the area dropping supplys to our troops (18 TONS in a RUBBER RAFT and in one trip
) So I stopped in to a port to see if the Japanese were using them. The Gunboat as you say "latched on" and I couldn't get rid of the pest. Fortunately I had some ammo for the deck gun and took him out. But it does seem like it's a bug.
Peabody