As I was reading this, I remembered the old days of duck hunting with my browning A5. I remember having to adjust the rings around the spring when I went from light load to heavy load shells. Does anyone else remember having to change them or am I just old and forgetful. It sounds, however, like this ejection problems is with both light and heavy loads. I am also certain that Browning would have pointed this out. I am a Browning fan and hate to hear about your troubles.
Another sub-gauge to look at is the Beretta 20 ga Ultima Turkey. I have never had a problem out of that gun regardless of what I shoot. Comes with rail for easy red dot installation.
Good luck with the 16.