DMAX,
Was the question: Did you try to restrike, refire the dud rounds been answered??
Your reloading method is excellent, checking each round in the loading tray. The Lee hand proper works very well also. I speculate you just did not seat them firmly on a few of them. I have done the same thing. Try a few more, if they do not fire, re chamber and fire them again. If they go off then that's the problem. Simple.
What I was saying was this.
Having powder of any amount in the case has Nothing to do with the primer igniting or not.
You can load a cartridge with NO powder. seat a bullet and primer and when the firing pin hits the primer it will go POP instead of BANG. There is enough force to move the bullet out into the barrel and you will have a squib stuck in the barrel. If you fire the next round and it has full powder, the bullet will jam into the stuck bullet and very bad things will happen.