It seems strange for your brass to contract or shrink back .0025" to .0035" after pulling the ball out the neck.

Usual shrinkage or contraction is .001" - isn't it?. Might depend on how small the sizer makes them prior to the expansion stage. Normal size difference between a sized case and a bullet, .0015" for accuracy ammo and .002" to .003" for hunting ammo. That means, they should be .363" to .364" after sizing & expanding.

Excessive contraction usually happens if the brass is a bit too hard. Sounds as if this brass requires annealing.

Just out of curiosity, what do the necks measure if merely sized, not expanded?