A couple of generic questions/suggestions, most of which I imagine you've checked. I use the 4000, so I'm somewhat familiar with the way Epson does things.
Were you getting the whole, intact image at reduced size; or a 6 inch partial image segment of the full-sized image?
If the former, that makes me think a resolution/size setting is off somewhere in Photoshop, printer driver, and/or RIP software. Are you using a custom paper size, and is it set up properly? Do you have it set to use sheets when you are using rolls, or vice versa? This has gotta be a setting off somewhere.
If the latter, think about a corrupt file or a print-head problem.
Latest drivers/firmware from Epson?
Using a RIP? Recheck your final output size/resolution of the image in Photoshop, and double check your RIP's settings.
Let us know what you find out.