I had a friend who had an AYA 20b boxlock XXV doing the exact same thing. Very difficult to open after firing.

It was so tough to open that he was worried about cracking the bar.

I took out the firing pins and polished the tips by turning them in a drill press against 400 grit paper, and that immediately solved his problem. Must have been a very small burr or something on the tip that was hanging up in the primer.