AI Ship troubles

[squalo111]

I've just created a ship lane and "seaport"  (with AFCAD) for the Queen Mary2 (by "Hama") and I have this problem:

when the AI ship reaches the RW, it doesn't stop on the RW itself (on my "seaport" the RW is terminal point of the lane), but goes away and prosecutes on a strange path over the ground, pointing to the starting dock. If I use another ship, this problem doesn't exist: the ship, as expected, stop at the runway and then disappears!

Any ideas?

Thanks
SQ111