It goes without saying, but a lack of a response regarding this issue is pretty unprofessional on their part. I know it must be frustrating on their side as well, but it's just something they have to make right.
Also, just a thought but would it help if they had a Duo on hand to test the disc with? Might not be worth it at this stage but for future projects perhaps lending the pressing plant a system for testing purposes would save a lot of headaches.