I never heard but I guessed that a stuck prop feathering relay is what caused the Dutch Dakota crash a few years ago. Can anyone confirm that?
Yes it seems the feathering relay was stuck and the feathering motor kept cycling in and out of feather.
The most simple cure if you are having difficulty holding the button in the out position is turn off the master switch which stops the feathering motor.
The reason the R1830 with the Hamilton Standard props has a feathering motor is the propeller feathering mechanism needs around 1400 PSI pressure to feather the prop..the engine oil pressure is approximately 85 PSI.
With proper maintenance and doing the proper run up checks it is a very reliable system.
Sure these airplanes are old, but I can not think of a more successful design than the DC3.
As far as flying one goes they are a million times more satisfying to fly than flying a modern jet that generally speaking was designed to be smarter than some pilots.