I don't use TM so not sure. I had an Escort Carrier in my sight. Distance under 2000m, speed 7knts and almost 90 degees to my bow. Perfect. However from experience these ships can turn on a dime.

So I set my angle between 10 to 15 degrees off her bow. Torp speed medium and set for contact. 1st torp is a dud, the next three hit home. Man, those carriers could blow up! What was the sea conditions like during your attack? Maybe that could be the problem? I made a torp run in rough weather and with despair saw my torps go under a heaving Cargo ship hull.