Prop feathering buttons were also a problem on the Lancaster I've read. Same sort of problem as you describe, and also one gent who found upon pressing the button on a particular engine all four went into feather.
But everybody knows about that
A common problem. We had a local lad killed with his nav in a F-111. One of the contributing causes was suspected to be a quirk with the type that all the old heads knew about, for they had all experienced the problem, and it was one of those things that you only did once in your life and lesson well learnt - if you survived. At the time of this accident the aircraft had been in service for 20 years, but this particular gem of information was not passed down to the new boys. It is now.
Ian, if you want to delve into the prop and its operation you may find the following of interest.
de havilland | 1944 | 2380 | Flight Archive
HamStd
deHavilland
HydGov
You can find a online copy of the pilot notes here (FB 6 model)
Pilot's Notes - De Havilland Mosquito FB 6