[MikeM]

On Random Mission, Medium, I track the remaining escort and merchant for an hour and I can see for sure they are the only two remaining ships in the convoy. At last I am far ahead enough to cut in across their course, submerge, and wait.

I fire two torpedoes and sink the remaining merchantman. The destroyer heads for me, weaving as described further up in this thread. I fire three torpedoes, one of which hits her. And then she splits into three images, two of which are depth-charging me while I file this bug report. The original version has sunk, and is recorded on the score-sheet. The two clones are identified as the same ship: USS de Haven.

Go figure, while I go back to dodge the depth-charges!

Edit: The attackers morphed into RCN corvettes while I was writing this up. But they still emerged from nowhere.