After Loading, My Sub Takes Damage!

[Scurvy]

I saved the game, after destroying two unescorted merchant ships, in deep water. When I loaded the game, I got an immediate message that I was taking damage. Looking around, there were no other enemy ships around. I was suddenly faced with 17% hull damage, that was irreperable, throughtout the entire patrol.

Is there a certain time when I should save my game...before or after an attack on the enemy?

I made it back to Freemantle, but I surely don't want to go through that again!!

Oh, and I have only the latest patch installed. No mods, yet.