Strange EL17 that you reckon the hand primer was the issue I went the other way as a hand priming tool allows you to feel the crush as you seat the primer where as a press with its leverage you can actually crush the anvil to the point that you will get spurious ignition of the rounds. I have been using a hand priming tool for the last 8 years and have great result but before I was using a press with a bit of gusto caused me to have all sorts of click bang episodes I find your post #30 most interesting.....

One tedious thing I do first is remove from each one all inside case primer hole burrs also uniforming all the holes to the same depth that way you are getting consistent ignition results once it is done you do not have to worry about it