You are overworking your brass. It's ironic to me that you admit that you don't understand total range of movement of the neck in an FL die with sizing button installed and yet you're disagreeing with Peterson about it. You aren't "bumping" anything in an FL die on the first or second resizing either.At any event, they claim the brass is being over worked. ...As for my shoulder bump it was adjusted to 2 thousandths. .. As for the mandrel part, I don't really understand TBH.
The line about not having problems in other brass brands doesn't really have any value, that another brand is better at being abused doesn't have any bearing on if the cases are uniform over their life or not.
It seems like you don't understand sizing die dimensions and set up, if you'd like to learn more this is a good video to watch. Start at 17 minutes at watch through 20 minutes for an explanation of cartridge headspace during sizing, and why you're oversizing brass if you're "bumping" on the initial resizing of cases that still chamber in your rifle: