I been thinking about that dented primer, but didn't fire scenario. Trying to diagnose it like it is someone with a rifle having that problem.

One possibility would be "light strikes" due to an old, worn, or broken spring on the firing pin. This an cause unreliable ignition. Sometimes it fires, some times it don't. It can be aggravated by mixed brands of ammunition as different manufactures use different primer manufacture and have different criteria for the primers they buy and use. You have several primer variables in all types of just rifle ammunition. Large Rifle primers, small rifle primers, magnum rifle primers of both LR & SR, standard primers and military grade primers and I'm no expert, just a reloader. There are probably more. These have different requirements for the strength of impact by the fireing pin to set them off and rate of burn and even that could fluctuate if you hit a hard primer with a light strike it may fire, not fire, or even hang fire.

I'll go double check my manuals to be sure if there are loads listed for both standard and magnum primers in 30-06.