DSF

We have a sawgrass sg400 printer, we've mostly been getting on ok but when we print artwork for bigger stuff i.e. t-shirts, we keep getting faint yellow lines through the artwork, when we press it, it comes out much darker. I've tried nozzle cleaning, test page prints fine, I've tried medium and high resolution prints, I'm now at a loss! Do I need to send the printer back for a replacement or is there an easy fix? we're using paper from an eBay seller but I'm not sure its that as when we print smaller artwork even a full page of it, its usually fine.

Any help very gratefully received, thank you!

in case anyone has this same issue, I managed to solve it! Its to do with the paper feed setting which can be adjusted under printer utility, I had to change mine to -6 and now its fine.