Unfortunately SH2 suffers bugs when saving
This is nothing Pacific Aces related, but comes from the original code....we can't solve that.
Anyway....the game saves your patrol whenever you exit normally. Then when going to the campaign again and trying to start the unfinished mission, it will tell you if you want to load the saved mission. If you click "yes", you will get back to where you were before exiting the mission. But you will get the bugs