After giving this some more thought, I bet the culprit is the paint itself. If you put a couple of heavy coats on and they aren't cured fully the clear will harden over it but as hard as it is DN is still flexible you would be able to dent the finish and it would explain the de-lamination of the finish. Also DN doesn't like to stick to some bills, 1.5 square bills in particular. Light coats of paint heat set should fix this.