Ah yes, that's done it! Odd how it was also happening with SH3C 2.5 at first though. In any case, the fixed files have solved the problem, wish I'd seen them earlier :p
Also, I know some destroyers only have hydrophones, but in my case NO DD was using active sonar, even in 1945 during a single mission i'd run to test it out, during which i intentionally made all the mistakes in an effort to get the destroyers to chase me, but no luck, I got away from them in 5 minutes flat, even with my engines at full and after blowing up the carrier they were protecting with steam torpedoes.
But yes, it doesn't seem to be a problem now, so no point complaining
Thanks guys!