This is a fellow's grad study paper, but the Germans had the same issue:
Wolves Without Teeth
The really amazing thing, is that the British captured a German electric torpedo. Shared it with the US, who then copied the torpedo (Mark 19) verbatim, errors and all, and unleashed its fury on the US submariners... Tang, anyone??...
USS Tang (SS-306) Naval History and Heritage Command, as an example. Others also experienced similar, and there are several boats lost without know cause, that may well have suffered the same fate.