Primers can and will go off if seated upside down. I've seen the go off on Dillons and Ammoloads. www.ammoload.com things to watch in primer filling in general whether it's a hand primer or automatic primer filling machines we had the old large Scharch primer filler machines these pre-date the Dillon primer fillers. the automated machines will swage the primer pockets with a die and then seat a new primer even if it were little tight these geared machines will flatten a primer even if you were seating with a good press you can flatten a primer. every now and then if you are going fast with the loader things get to rattling and it will flip a primer kind of looks like it was mushed not the rounded edges as normal. the other possibility is the primer was loaded in the primer tube or tray upside down been there done that, the old CCI primers the ones with the hard cup metal had problems seating in Dillons back when since that time CCI has corrected the issue. The Ammoloads had scatter shields on them at least ours did. Remember large rifle primers are .008 taller than large pistol primers.
Thanks for the info.
I've been reloading since I was 12 and have seen just about every type of primer seating problem, upside down, sideways and have punched them back out after I put a drop of gun oil on them so they wouldn't go off.
I've been using Dillon machines since the 90's and started with a Square Deal B before getting a used converted 450/550 and still have both including the 550B. I have 4 shot shell presses and 2 rifle presses. So I know the difference between a rifle primer and a pistol primer height.
But when a company miss packages a large rifle primer in a large pistol primer package it is hard to distinguish between them.
Again thanks for the information.