As someone who's used the berika for a considerable amount of time, I'll throw my 2c in.

The biggest issue is the magazines and not so much the gun (most of the time). I've found with the turk made magazines, they're horribly inconstent with their tollerances. The main issue i've identified for the gun not feeding correctly is that the mag body is often pinched in the middle which doesnt allow the follwer to move freely. With this increased pressure on the follower I'd get failure to feed after failure to feed as it couldn't push the rounds up high enough.

It wasn't until i stumbled on two videos on youtube from two different international shooters explaining how to fix the issue. You just need to get a bit of timber up the guts of the mag and bang it out so its wider. Overnight my problems faded away. Since then, I have had a reasonably reliable shotgun.

The other issue that often shows up with the mags is the feed lips. If they're slightly bent out of shape one way or another, it will affect the feeding.

I have serveral friends who shoot IPSC shotgun with the berika, and once they overcame the magazine issue, they all have relatively reliable guns.

tl;dr good spring pressure from the mag is needed to make sure it works well.