Thanks for your post Jimbuna, but I'm not trying to "teleport" ... I actually completed the assigned mission and afterwards reached Wilhelmshaven but then I experienced the problems described above.
In the interim, using the last saved game, I tried to end the mission within the 25 km radius, but outside the immediate vicinity of Wilhelmshaven harbour. It showed the "Exit Patrol" and I was able to do the awards, promotions, etc. However, after getting out of SH3 then re-entering it, the mission showed as "Dead" as if I had done a "teleport".
For some reason, it is like the game is not recognising Wilhelmshaven as the home end point, but treating me as I'm raiding an enemy port.
