Your die needs to be pulled to bits & the brass that is stuck on it needs to be carefully removed by polishing with autosol etc.
You need to lube the brass more when sizing it.,
It is possible it is a little soft after annealing making the brass easier to pick up onto the die.
If you can see up into or down into the die you will see brass stuck to it in the neck area.
Until it is removed it will continue to mark the neck which is undesirable
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