I had a similar problem with the Harman 17"x25" FB Glossy Al paper as you are having with the Ilford paper until I figured out a method to load the paper that fixed the problem:
First, contrary to what you may have been told, use the sheet feeder, not the rear or front feeder. After the paper is in the sheet feeder, nice and square to the edge, push the advance button (the bottom one on the printer manual control). That will suck the paper into the machine to the starting point. At this point, the sheet is now bent a little from the leading edge. Just let it conform to that curve for a minute or so. It'll take that long to get your print all set most likely anyway. It's now conforming to a gently curved path that won't rub against anything on the way into or through the machine.
Finally, set the thickness at 5 and gap at "wide." Print. You won't have to trim paper to a narrower width either.
Because your machine is new, it may take a few of the large sheets to smooth out what will first appear as little, obscure pizza wheel tracks, so I'd try this first on a few sheets of cheaper paper if you can. For me, it only took about 3 sheets, and from then on it was fine. Now, there are no marks at all, even on large solid black areas on the supposedly fragile Harman Glossy paper.
Let us know if that works for you.