I can't tell you why those rounds misfired, but as to the apparent light pin indents, a primer which fails to fire will always show a more shallow indent than one which does fire. When they fire, the internal pressure drives the primer cup back to the breech face and sort of molds itself around the pin tip. Obviously that pressure molding won't happen with a misfire so the indent looks more shallow. You can see that for yourself if you'll kill a couple of primers by soaking them with WD-40 for a few minutes before seating them into an empty case, then compare the indent of the dead primers to a couple of live primers. Of course, do exercise care, a primer alone makes a very loud POP with enough muzzle blast to blow through several layers of cloth at the muzzle.
But it is also true that H&R/NEF long guns due depend on trigger over-travel to raise the transfer bar and that can be troublesome if you have a very light trigger. But my guess would be defective primers rather than defective rifle.
