Interesting no answer to this but I may have a solution based on a problem I ran into while working my M3K over. Full disclosure, I just picked up my gun and tore it completely down for cleaning and adding some MOA precision parts to it. Anyway I stumbled on your question looking to see if anyone had the issue I was having.
When swapping out the bolt release button and the shell stop or carrier latch extractor as the owners manual calls it, I found a short pin inside the carrier latch extractor spring that limits the travel. Why Stoeger added this is beyond me as it appears it’s n