If that is a possibility, then have another good shooter shoot the gun, and see if he gets the same result. Then you will know its something the shooter is doing.
My wife was flinching at the last moment when she fired her shotgun. I caught it when I stood behind her and looked over her shoulder while she fired at stationary clay pigeons on an embankment. At the last second, she would look at the front sight with her left eye. Once we got her to close that left eye when shooting, she began hitting flying targets( and those stationary ones, too) regularly. I started loading her gun for her, and sometimes omitting to put a shell in the gun. That broke her flinch quickly, as she could then easily see what she was doing, jerking the trigger on an empty chamber.
Sometimes a stock needs Cast off to fit the face properly. Anticipating recoil by lifting the face off the stock, is much more likely a cause of wide shots, than "sneaking a peek"! On factory stocks, often the comb is too high for some shooters, or the LOP is too long. :hmm: Lowering the gun too soon can also cause problems, and if the stock is too long, neck cramping is common as a source of problems in lifting the head off the stock too soon. A gun should be mounted to the shoulder and your eye looking down the barrel at both sights, at the same time. If you have to lower your head to see the sights, or move your head right or left, You are mounting the gun incorrectly. The stock may not fit you, and that will be the root cause for why you are mounting it wrong, but you have to mount the stock to your face and shoulder at the same time. I was re-educated, myself, by a good friend and Champion Shotgun shooter, to thrust the stock forward, and bring the rifle or shotgun up so I was looking down the sights as the gun came back to my face and shoulder. No dipping my head!
When I studied combat pistol shooting, with John Farnam, he trained us all to move the pistol up to our eyes,and not lower our heads to the pistol, using a two-hand combat hold, or grip. I smiled, remembering all the effort I had put in learning to mount my shotgun and rifle the same way. :surrender: :thumbsup: