Good evening to you!! It is possible that it is both. Most autoloading shotguns need a minimum of 1300fps to function reliably. Most have a break in period of roughly 500 cycles. You can speed this up by leaving the bolt locked back when not shooting it and racking the action every once in awhile. Hope this helps. Have a good rest of your day.
🇺🇸🇺🇸 'Merica' 🇺🇸🇺🇸

Hi Nathan, the issues you're experiencing with Fiocchi buckshot may be due to the low recoil of those shells, which can sometimes prevent proper cycling in semi-auto shotguns. It's also possible that your shotgun is still in the break-in period, where it may not function perfectly until it has been used more extensively.
Stay safe & have a great day!

Probably both! Most semi-auto shotguns need shells with a min velocity of 1300fps up to 1600fps for the first couple hundred rounds. I’ve been looking and probably the Fiocchi shells were under 1300fps.

Hi Nathan and welcome. A method I have used that has allowed me to cycle even low brass loads is to store the shotgun with the bolt locked fully back. This will condition the bolt spring to allow full rearward travel to cycle most loads no issue. This prevents you from a lengthy break in period. Cheers, stay safe and enjoy!

It is highly likely a combination of a break-in period and the low-recoil nature of the Fiocchi shells causing the cycling issues. New semi-auto shotguns, especially inertia-operated ones, often require 50–100 rounds of high-velocity (high brass) shells to break in and loosen the action before they can reliably cycle lighter, low-recoil, or low-brass loads.

Both more than likely. Most semi auto shotguns need shells with velocity of a minimum of 1300fps not to exceed 1600fps for the first couple hundred rounds. The Fiocchi shells may have been under 1300fps.