Yes, the feather button frequently failed to pop out. You can call it a holding coil if you like; as an electrical switch being held in place by an electric field, it was a coil; it was also called a feather button, and was named as much in the aircraft flight manal and the maintenance publications I used.
Now, now, Guppy, don't go getting all bent outa shape.
The feather button assembly also contained a holding coil inside, which held the feather button in (electrically), and when the propellor reached feather, the holding coil was de-energized, and the feather button released.
A simple and quite reliable system, seemingly contrary to your previous comments...
I have plenty of hours in DC-6's, Constellations, and a few hours in Stratocruisers, and never had any problem whatsoever with the feather button assembly.