I think i might know a video where this or something similar happened on camera for Hickock45. Around 8:30 in the video is where he has a very similar happen to him.
He talks about having a couple rounds that took a couple strikes to go off. This problem was from bad ammo more than the gun.
He hypothesizes it might be an issue with the magazine, but basically the gun just did not pick up a round in the middle of a magazine, not sure if he ever had the problem again.