Corrupt saves and ghost ships after convoy attack

[karamazovnew]

After attaking countless convoys in the shallow waters of the British coast, I've learned a few valuable lessons:
1. Don't save until you get to at least 30km away from the victim's wreck.
2. While loitering around (again, a 30 km radius), don't attack any ship of the same type as your previous victim. Even if it sinks, you won't get any credit for it. For example, after a very succesful attack on a convoy I sunk a Large Cargo and a Large Merchant. I "exited" through the back of the convoy. As I was waiting at a full stop (mines around) for the convoy to get BVR, 2 more ships appeared near me, you've guessed it, a Large Cargo and a Large Merchant, same speed, same direction. Sunk again, no dice.

So far this has been true for any ship sunk in shallow waters, in convoy or solitary.

Anyone else with this problem? I'm using GWX3 .