I'd like to suggest that you fire a single shot, at a clean sheet, at 20 or 30 yards.
More than one shot per sheet just muddies the waters.
Then post up a photo.
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I tried it again over the weekend with a new box of ammo and no issues this time.
Pattern appears real good. Didn't seem to notice the ringing sound either, but likely was the loose rib it has.
Will try it out on some clays when I get a chance.