[UKönig]

There is a simple, real life explanation to the problem you are (We all do at some time I guess) facing, regarding torpedos.

German torpedos were crap. In the beginning...

Let's look at the evidence...

In terms of complexity, the average "fish" weighs 1.5 tons; is almost itself, a miniature Uboat.
We have the T1 - in service since 1918. But uses compressed gas to propel it forward, leaving an obvious trail than any competent watch should be able to spot and react to in time. Not all the time, but nothing and nobody is perfect after all...
Still useful in night attacks, and choppy weather with bad visibility, but to fire in smooth seas with clear skies is to invite a miss.
By 1939, I would imagine that the Kriegsmarine would have solved a lot of the problems of the 1918 model, but they still had troubles with the depth gear. If stored for too long, it seems the spring inside becomes partially unwound or unspooled which loosens the hydroplanes responsible for holding pitch in the water, and thus, your torpedos can run 5 - 10 meters lower than what you set it. We also have bad magnetic influence detonators. Can blow too early, too late, not at all, or even by hitting a large enough wave, on its way to the target.
Next we have the T2/3 - improved versions of the T1. Wakeless now so to as hide the firing sub. Better range and yield. Early T2 still had depth keeping issues, but by 1943 depth gear problems had been fixed. Mag fuses more reliable. It was the kind of reports that kept coming across Dönitz's desk from his uboat captains "in the field" about the high failure rate, until he held the feet of the torpedo manufacturers to the fire (probably literally), until they categorically fixed all the faults found thus far. But in the meantime, U-captains had to just 'make do'...