You are saving your games in a wrong way.There maybe multiple mistakes in stock SHIII as well as GWX if you save your patrol:
1.Close to other ships.
2.Being submerged.
3.Close to land.
You should always save your patrol far from land (over 250 km),without having visual or sonar or report contacts with other ships,and in surfaced position.Generally speaking,there should be clear map around you and your U-Boat must be surfaced.
Hope that helps.Good Hunting.
