Don't know the issue but, here's some things to ponder-
NF could replace this scope with virtually no issue what so ever tot he company, multi million dollar companies don't worry about 1-2k here or there... But if it checks out good, and they have shot it and it also checked out, what would sending you another perfectly functioning scope do when it will be just the same? Nothing- That's why they are not replacing it- There rep is no bullshit, they don't win at the championships over and over because they build shit and don't stand behind it if it fails...
Gunsmiths are gunsmiths, scope builders are scope builders... The only thing the two products have in common is they both have screws... Be very careful when a gunsmith jumps to the conclusion of it being the scope, 'cuase he likely don't know dick about a scope...He'll tell you he does, but he doesn't, unless he's built scopes also...They are as similar as the moon and the sun, both planets, both in the same galaxy, after that, not even close to the same, how many gunsmith's are optics engineers? Exactly...
I don't know how much poi you have, and I'm not going to read through all of this, but I believe the NF rep has mentioned less than a 1/4 moa in the history of the company ever... Lets just for arguments sake say he exaggerated 2x over, ( he most likely DID NOT) as I know him personally, but lets pretend he misspoke, that would mean theoretically, 1/2 of a min of poi, if you have more than that, no way it's in the optic, and if you have that, still very very unlikely its in the optic, and if they checked it twice, simply no way it's the scope, they'd see it ( a blind monkey could with their equipment) and thed's fix it, send you a hat and an apology, and off you would go. That's how top tear companies do business- I don't care if guys on hear have an ax to grind with NF or not, but NF stands behind their product 100%, but with that, if it doesn't fail, they have to stand behind it too, or you will not find the issue in the rest of the shooting system, as they will be giving you false info...
Here's what I would say is for sure in my internet driven worthless opinion, but since that's what we do when we aren't shooting:
That scope is not pointed in the same place after the recoil of each shot, as in, it's moving, somehow, unless it's in the actual rifle...
Would be great to hear you found the issue, and all of us could be a little smarter for our next go around-
Best of luck