Ship trap in Oldtown

[tos1]

Player's fleet can accidentally go upstream of the Oldtown and it never return to the sea again.
This happens when you intentionally repeated to land/sail toward landing points that are nearer to the upstream.
Attached image of v8.1: (1) My ships are sailing on the sea. (2) Landed at a LP. (3) Another nearer LP that is in the wall. (4) Landed on the bridge-like field. This sometimes happens but is not indispensable to reproduce the situation. (5) My ships were accidentally put to northern side and cannot be out to sea.

That happens also in v7.11 and the image shows a stuck ship. When I pass by it, it makes noisy sound (often-heard on the sea) struggling to move but it is in the same place whenever I visit there.

- Computer specs:
Laptop, Win8.1 64bit, Core i7-4600M 2.9 GHz, 8 GB memory, GeForce GT 730M

- Game version (and steam or downloaded):
AWoIaF v8.1, Warband v1.167 downloaded
(AWoIaF v7.11 has the same problem)