But it's the case with any semi-auto round I've played with, that chambering a round repeatedly will drive the bullet back into the case some.
it's a fact that this can, and does happen, but it doesn't HAVE to happen. You can, and factories used to build their ammo the "right" way so setback wasn't much of an issue. Today, that isn't the case. Ammo makers build their ammo to be "good enough" for a few chamberings, as this is all most people will do.
One fellow I know bought two boxes of Federal 185gr JHP in 1980. He kept the last 7 rounds (one mag) for home defense, factory to avoid any legal issues with handloads. He kept that mag of factory ammo for 20 years!!!!
Those rounds were chambered hundreds, if not thousands of times over the years, to the point where the nickel cases had brass stripes showing through the nickel plating. Rounds were repeatedly measured for setback. NONE ever setback. He did, eventually fire them and every one functioned perfectly.
Based on this, I believe that ammo CAN be made that won't set back during normal use. The fact that most ammo isn't made to do that anymore, doesn't mean it cannot be done. At least one maker used to cannelure their cases, right below the bullet base, which prevented any setback. They don't do that, nowdays...You also see it on some old GI .45acp ammo....
Setback CAN be prevented. Its just ammo makers today (usually) no longer bother with the added effort & expense.
The ammo you have was "damaged during shipping", the retailer should not have sold it in that condition. Contact them, FIRST, for replacement. DO NOT SHOOT ANY OF IT!!! Do not shoot the "good" rounds, keep them all intact, AND the boxes and turn them in for replacement. Turn them back in to the retailer for replacement, and let the retailer get their money back from the shipper/distributor they got the ammo from. If possible. If the retailer won't act, go to the manufacturer, and ask for help. Being able to send the maker all the rounds and in the damaged boxes (if they ask for them) would be a plus.
To be fair, a slightly damaged box USUALLY doesn't mean damaged ammo, but in this case, you have clear evidence of the ammo being damged (bullets shoved deeper into the cases), and I believe you are due a replacement or refund.