Did you yourself paper tune it, or did someone do it for you? You have to tune your own bow, because your release style and form are unique to you. It's just like sighting in a rifle. Don't ever trust one sighted in by someone else, always do it yourself. I guarantee you it's a tuning issue. I checked Carbon Impacts website, and without knowing exactly what arrow you are shooting, I can't relay the spine information. I would suspect they are just a touch stiffer than 400, probably like a 360, but I am merely guessing at that. Your 400's should be right on given the 27 3/4" length. Any longer and you'll need 340's, so it's possible you are just a tick little bit underspined.

At any rate, head back to the shop and paper tune the bow yourself. Get help w/ the adjustments and such if you need it, but you be the one doing the shooting.