Neck sizing issues...

[Treetrimmer]

From what I think is going on try and adjust your neck sizer die down.
Mark the threads and lockring and then move the die down very little at a time.
If your shellholder is already hitting the die and it is hard to cam over, you need a different die or shellholder.
your neck sizing die should bump the sholder back just fine if adjusted properly hope this helps .