Hi,
Thinking about that post I made on aligning dies... If you're using a full lenght die and setting the shoulder back in the process, you may not be able to get the die aligned and still have the proper amount of shoulder bump. As you adjust the die in and out to find alignment the amount of "bump" will change to (possibly) not enough, or too much. I use this procedure on a Redding Competition neck die and can adjust the amount of neck sizing done with the micro adjust on the top of the die to compensate for having backed the die out of the press a bit. Using a generic neck die will cause the same problems as using the full length generic die. If the Redding Competition has an adjustable neck and shoulder bump in their full length sizer, I don't know. I'd wager it's an adjustment for the neck part of the sizing and the bump is adjusted with the die body.
Coyoter