i am printing 24x36 for a gallery show. My borders are specified as 2 inches all the way around. I check the box to have the image centered and fit within the borders. The prints come off the roll ar anywhere from 34.5 to 37 inches long and borders are uneven. I print on an Epson sc p9000. All firmware is up to date. Epson has been no help ... they just say use another program to print . Help!
Sounds more a printer problem. (I don't know how your prints length can range from 34.5 to 37 inches)
There is a changing offset amount in printing. That is why there is trapping in offset printing. Usually it is less than 1/8 of an inch, but I have seen printers go off a larger amount.
If you want to try another application then try taking your photoshop document and save it as a Photoshop PDF. Then open it up in Acrobat and print from there.