NGC calls these mechanical errors. Contact customer service and they'll let you know how to get it fixed.
I had piece where the label was printed with the wrong date. They had me send it in and they corrected it. Reimbursed my shipping as well, but this was 5 years ago, so I don't know if that policy still stands. I do know they don't want these errors floating around, so they will try to get it fixed if you let them, it obviously is negative to their brand.