I have a Grey I've had since he was a baby and he was DNA'd in his clutch and determined to be a male. My vet (an experienced avian vet who has seen lots of Greys) swore he was a female, due to markings and other features. So, I DNA'd him again a few years later, thinking maybe the DNA tests of the clutch mates got mixed up or something. This time I used blood instead of the feather, and once again he is determined to be a male. But, I still look at him with the probability that both tests were wrong. I wouldn't think so, but I suppose it could happen. My Grey is marked like a female but is one of the largest Greys I've ever seen.
I can't wait for your results. I'm hoping it's a girl. Good luck!