I'm having the same issue. I bought the HP 5520 last month and within 2 prints there was a loud grinding of gears sound. over and over so I exchanged the printer. The 2nd one has been great for about 2 weeks when out of no where, yesterday GRIIIIND! it's loud and startling... it sounds like gears are not lining up properly and it's trying to.
I read the description to clean the rollers, which I will but I'm not sure how these smooth rollers could cause the gears to click and grind loudly. Please advise.