"The minimum recommended load for the Stoeger M3500 is 1 1/8 oz. If you try to cycle loads lighter than that, you will end up with cycling problems. Sometimes, the M3500 might spring back to action after breaking in. However, the gun is not at fault because it can’t cycle lighter loads. In fact, manufacturers build the M3500 for cycling heavier loads. If you frequently require using the gun with lighter loads, you may not actually require a 12 gauge chambered gun designed for up to 3.5” ammo. Cycling Stoeger M3500 problems with 2 ¾ rounds are very common. However, using it with heavy 3 ½ inch shells for the first few hundred rounds will help you to loosen up the gun.
After purchasing a brand new Stoeger M3500, you may be eager to test it out immediately. The jamming problem is common with the guns during the initial hunting phase before breaking in. The general rule is to put one load in the chamber and two loads in the magazine tube. The hunters should easily fire the shells one after another. Sometimes, you may just hear a click and it won’t fire. Ejecting can also be a big trouble. Even though this can be disheartening, you can easily solve it by cleaning the gun. Guns straight from factories accumulate gunk and you cannot use them out of the box. You have to disassemble it and clean every part. Lubricating it with oil is the next step. You should always use Rem oil to achieve desirable results. Sometimes, break-in is not necessary to resolve the jamming problem."
This was found just doing a google search for known issues with this shotgun, seems a good cleaning and just breaking it in and not maxing out the mag will save some issues.... Initially....