I am having the same problem. The print margins (according to specs and the reason I purchased the Phaser 8560) are supposed to be 5mm all around.
However, recently my docs started printing off-centrer, with the right margin being wider. I am a graphic designer, and this affects my documents (regardless of their margin settings)., i.e., margins could be set at 1/4" (well within the printable area) and document still prints off-center, to the left.
Service technicians have told me they can't fix this since there is no adjustment they can make. One replaced my Tray 1, thinking it was out of alignment, but that did not solve the problem.
This is a critical issue for me. My printer is only about 2 years old with less than a 17,000 page count.
I did do the firmware upgrade.
I realized that the answer to the margins, at least for simple things, is not to create margins in PhotoShop. If I just make the picture the size I want it centers fine.
I do have another question.
Assume I print a picture on Xerox Glossy paper and have it framed behind glass.
A picture on Epson Glossy printed with an Epson Ink Jet claims 200 years.
But I haven't seen the equivalent for any Xerox. I spoke to someone at Xerox some years ago when I had a color laser and I was told that there were too many kinds of paper that could be used. So they did not test it.
I have a high end Epson but it is a pain to use and it is slow. I find using the Xerox printers are faster and I don't have to deal with icc profiles.
I am on my third Xerox. This one is a refurb 8560. It produces really nice color and all that.
But it does not center the margins on the pictures I've printed.
Margin errors occur in both Tray 1 and Tray 2.
I set the canvas to 5 X7 and the item to a lesser size.
But both the top and side margins are not equal.
The same thing happens with larger paper (8.5x11) in Tray 2.
My previous Xerox which was a Laser with toner never had that problem.
I'm using Photoshop CS5.
I'd appreciate any advice.