Hi John, The lines are running vertically on the paper. I also suspect it's either wheel or the pointed base of the printer. I've tried cleaning the base & wheels with cleaning liquid but no use. I have two types of paper, one thinner 100 gsm and other thicker 120 gsm.
The issue is, lines are consistent & more visible on phone covers after sublimation done using thinner 100 gsm paper. However, sometimes faint lines show up when sublimated with the thicker paper and other times they don't show up. But end result quality/colors is much better with thinner paper so I'm more keen for printing with thinner paper.