New owner. Problem when shooting suppressed. Need HELP please!!!

So I finally took my new PS90 to the range. I had never fired it and have only changed the barrel shroud with the Huntertown Arms shroud so I can use my suppressors while waiting for my SBR stamp. The shroud switch was a breeze, no problems and I'm pretty good with stuff like this so I'm confident in the switch over. At the range I had two mags loaded with SS197SR. Made it through 35ish rounds with no suppressor and all was well, shots were consistent at 50 yards and grouping well after zeroing my Z-Point. Decided to try out my Spectre II, have used it a lot on my various 22s and it's working great. The very first shot fired but after that nothing would, and a look at the chambered rounds showed no primer hits. Tore it apart at home and finally found that the one round that fired suppressed, the neck and shoulder of the brass had separated from the body of the brass (which had ejected).

Now I'm pretty familiar with shooting suppressed, had the suppressor screwed on right with a spacer needed for this shroud, so I'm confused. Any ideas why the neck and shoulder would separate? Thanks for any help.

Jason