So, I went and pulled my P-10C out of the safe and sure enough, the striker when pushed does rotate and lock in place. Then when I hit the slide release. the gun gives zero Fs and goes straight into battery even with the displaced striker. Overhand racking the slide also goes into battery with the striker pushed over.
Then I watched the video again. 1:37. Hey buddy, don't ride that slide. Let it go.
1:58. Once he stops riding the slide it goes into battery, but then he keeps pretending it didn't.
2:16, yup, there's the lose back plate. So, how are we getting to the lose back plate. Yes, this can be replicated, but there is more going on than he suggests. Now, it's important to baby the slide forward so that the striker catches on the frame instead of being forced back into alignment. That is important because it is what causes the back plate to unlock. With the slide closed, but the striker forced to it's full possible extraction, the striker block is closed. If the striker is the freed,it will travel it's full distance and hit the striker block, compressing the whole striker assembly briefly forward on the spring, unlocking the back plate for a instant. If one is pushing down on it when that happens you can force it out of alignment enough the slide won't close.
Two simple solutions: 1) Stake the cover plate or roughen and edge so it doesn't slide freely. -or- 2) Don't ride your slide