I know Benelli has had a similar problem with the infamous "click" misfires. As it turns out, this problem was caused by the Montefeltro bolt that was not "forcefully shut", and the firing pin barely hit the shell. This bolt rotates until it is fully seated/shut. Owners were having trouble when walking around in the woods, they bumped the bolt and rotated it the smallest bit. This causes the "click" due to the fact the bolt was not fully against the shell. I don't have a Mossberg, so I can't say that that was a contributor. Best of luck......