Well, it has been a problem in the past, it was minimized on the Loadmaster by adding a die in station 2 to center the case, as priming is done on the TOP of the stroke.
That does not work for presses that prime at the bottom, like the Pro1000, ABLP, or Pro6000.
There is a common mod to deal with the off-center 9mm case in the 19s shell plates.
It's simply a wire glued in the shell plate case cavity to keep the case from going too far into the case cavity.
Attachment 306725
This fix is to minimized primer flipping during the primer seating operation.
jmo,
.