I may have finally found the explanation to something that happened to me!
You see, I had two German destroyers do the same thing. I "picked them up" just off Helgoland and they followed me dutifully halfway across the North Sea. They'd disappear when I used TC above 256 or so, then reappear in the exact same positions relative to my sub when I lowered TC.
I briefly toyed with the idea of keeping them there - they might come in handy in finishing off convoy stragglers and lone escorts
- but thought better of it. With my luck, we'd run into the Hood and the poor surface boys of the Kriegsmarine would be history.
Anyway, it's not just enemy destroyers, and the fix is, as already mentioned, to save/reload. When I did that, the two German destroyers were still there, but they promptly did a 180 and made a beeline for the Vaterland
