Obviously I can’t prove this, but would postulate that in the one cartridge that didn’t fire until a second hit the primer was seated just a tiny amount shy of deeply enough and the first blow finished the job. Otherwise, the revolver may have needed cycling to get the dust off.
My most extreme treatment of primers tale was a couple of bricks that got rain soaked on the loading dock of the local distributor. They were very iffy a couple of weeks later in our tuned PPC revolvers when we tried them in, so I just threw them on a shelf and forgot them for 30 years. During the primer scare recently I tried them in some 9mm cases for my S&W Model 39 and they all worked perfectly. Go figure.
Froggie