Dud Torpedoes

[Sayeret]

http://www.ww2pacific.com/torpedo.html

[OldRecon]

http://www.ww2pacific.com/torpedo.html
Kriegsmarine also had same problem with magnetic pistons early in WW-2.
The battleship Warspite amongst others being torpedoed to no effect at Narvik.
British FAA also had same problem with magnetic pistons, which was instrumental in their decision to opt for contact fuses for the attack on the Bismarck.
There was also several instances of torpedo launching ships hit by their own torpedoes after hangups in their steering mechanisms (at least one British cruiser and a US submarine being lost that way).
Post WW-2 Royal Navy also don't seem to have been too happy with the Tigerfish submarine torpedo, relying on unguided WW-2 vintage torpedoes (MK-21?) for the sinking of Argentinian cruiser General Belgrano during the Falklands war.
One US Skipjack class nuclear hunter-killer submarine (USS Scorpion) apparently also was sunk by one of its own torpedoes (apparently caused by vibration sensitive propulsion batteries leading to uncontrolled start-up of torpedo engine).
Last Russian cruise missile sub kursk apparently was sunk by one of its own torpedoes exploding on board.
Torpedoes are apparently complex weapons to engineer.
As an example a Norwegian resistance saboteurs that tried to make a workable mini-torpedo for attacks against German shipping in the fjords, worked for 3 years on the problem and didn't come up with a workable solution until shortly before or after the end of WW-2 in Europe.