Not to insult your intelligence, but when you zero'ed her, did you follow the zeroing instructions carefully in accordance with the user manual?
If not, yes there can be some serious shifting issues.
Next I would inspect the mount, and locking mechanism and and the screws.
Good luck. If you need any assistance you are more than welcome to call Night Goggles or TNVC, and we can even put you in touch with the folks at Steiner if need be.