Happened to me a couple of times before too. It's the save game bug I'm afrraid and there is no way to my knowledge of rectifying the problem. Go back to a previous save if you can (sometimes these are corrupt as well depending when the first corrupt save occured), other than that you will need to go back to the in port save thus losing any progress made during the patrol. All this is assuming of course that you haven't applied any mods during the patrol. If you have, disable them and the save game should load properly.
Nemo
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"I'm afraid there is no disguising the fact that King's obsession with the Pacific and the Battle of Washington cost us dear in the Battle of the Atlantic".
Sir John Slessor GCB, DSO, MC, DL
AOC-in-C Coastal Command RAF
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