yes. that is the reflective 'mirror' that your ion's eyes use in part to detect the paint in the chamber. It will still work well even if it is scratched or a little paint gets on it, but if it is removed, it will need to be replaced.
I doubt that sticker would be why. It would only cause your eyes not to work and your gun not to be able to function properly. Chopping could be bad loader, bad detents, bad paint, bad paint/bore match.
And the ion does use break-beam eyes. The only reason for having the silver 'mirror' (i think), is so that if broken paint or debris breaks the beam of the eyes, the 'old' reflective system can still be used, since both nodes transmit and recieve information.
Gwar: Paint that sits in the sun for a long time, or is very old and dimpled shoots very badly and will chop a lot. Also, check that your gun battery is good, and that your hopper batteries are good/that there is no debris on the inside of your hopper.