I agree with checking all screws for tightness: action, bases, ring screws. As someone mentioned above the scope rings may be loose or not torqued tight enough. Check to see if the barrel is truly free floated, as the Axis stocks tend to be a little flimsy up front. Also ensure the stock fore-end is not touching the barrel when you load up on it to shoot. That Nikon scope should have no problem holding zero.

Have you shot groups with the ammo you're using to see if it even groups?

I too prefer my barrels to be a little fouled vs too clean. I clean maybe around 400 rounds or so and have not noticed any accuracy issues.