Early in the war there were many malfunctions for german torpedos, and later the US have experienced the same problems. If you are frustrated, then think about how the real skiippers were frustrated
Only thing you can actively do to reduce misses is to make your torps hit at 90° and not deviate much from such a hit angle. Then always consider the draft of your target in order not to make torps pass below target and not explode, don't set their depth to the draft limit, but above...
Still magnetic torps may not explode or explode early, and impact torps may not detonate on impact. Play from 1943 and beyond and you will experience less duds.
Then, with SH5 it's the question if your game is patched correctly because the stock game has a lot of torp malfunctions due to *game bugs*. You can resolve this one with a good mod configuration. TWoS megamod is best probably and you are on the safe side against bugs.