Unwanted transfer

I have had this happen to me more than once. I am sailing out of Pearl, and suddenly I find myself down under. Then, I leave from Brisbane, but when I return there at the end of the patrol I can not "end patrol" only refit. I then sail to the other ports and find that I am assigned to Freemantle. First why am I being reassigned to a new port from PH without requesting a transfer? Second, why does the game start me at a different port from where I am assigned? I have tried to do a search on this topic, but I was unable to find a thread that addressed this topic.