A few things it could be:
First is brittle brass. It happens, I use an annealer for older Lake City 5.56 brass because when I try to make 300 BLK or 7.62x40WT it splits way too many necks. The next thought would be improperly made brass.
Next, clean your chamber (and bore), sticking brass in a dirty chamber and running a suppressor with a wide-open gas block can cause an over-gassed situation. With the carrier timing not unlocking properly can cause some pressure, but usually you would see that on the brass (besides the necks and breaking), how do the bottoms look? Flattening of primers, extractor marks on the rim, ejector swipes? Any bulging near the base of the brass?
Are you full length sizing the brass or just pushing the shoulder back? It would probably help to bump the shoulder about .004" so that they cycle but don't work the brass too much. I have to say though that I have 4 6.8's and its a bitch to keep the brass separate for each barrel lol.
So first thing, clean the gun, clean the brass well, resize less, check pressures, and then through the Federal brass in the trash can and get SSA lol.