Actually this can be caused by any number of things. Here are a few examples.

You may be twisting your grip a bit
You may be pulling the string into your face too much
You may need to get your eyes checked (not kidding - poor eye sight can cause all kinds of problems).
You might have a spine problem
Could be a draw length problem.

You may simply find this bow never has the pins in alignment with your string & rest.....I have seen bows that shot perfect paper tears but the pins set outside of the line of the arrow & the string. If you shooting good & having no problems I just don't think Iwoudl worry too much about it to be honest.

Does the string contact your face at full draw. If you're not tucked in tight it will throw your angle of sight off to the side. I shoot fingers though and don't have any experience with releases. I find my best form comes when the string touches the tip of my nose. Like others have said, your grip has alot to do with it too. Is your arm locked? Open your palm on the grip, lock your elbow and rotate your arm so that the inside of your elbow is plumb. If the inside of your elbow tilts in toward the bow, bad things can happen.

Oh and also, My pins are NOT perfectly aligned with the arrow either, I think some offset is common.

Thanks guys. Looks like the general problem is a form issue. Makes perfect sense. I am conscious of trying to maintain consistent form. I try to have the string touch the centre of my nose and tuck my thumb under my jaw. Perhaps I am getting some inconsistancy each time I strap on the release aid and that is adjusting the distance I have to reach for the trigger? All this gives me something to work with anyway. I'm now pretty sure it isn't equipment related. Good to hear that a few of you have the same sort of offset in your pins too.

Have you checked for your eye dominance? Is it the same as you are handed? If not go with a bow that is orientated for your eye dominance not by what is your dominant hand.