MFC7820N has accordion pleated paper jams in the rear of the printer. I have removed and cleaned every part of the printer including roller feeders and reassembled (correctly). Any suggestions?

I had the same problem for a few days. The paper only makes it a couple inches through the last rollers entering the output tray and the rest of the paper forms pleats like accordian bellows. This started to happen nearly every time. Changing the paper, toner and drum as well as cleaning do not help. Lift the scanner, which covers the output tray, and watch to see that the rollers at the back of the tray are actually turning when printing. If they are turning, then the paper should come right through into the output tray without forming pleats. You can push down on the four spring loaded bottom rollers at the back of the output tray to check that they will let paper through. My printer stopped making the pleated sheets.

I have MFC7420 and 7220 and have the same problems. So bad, almost every paper was jammed like an accordion. SoI opened the back panel and unscrew the part with the small roller and take it out to clean them. I found there is another roller on the ceiling of the same area and I cleaned that area as well and roll the rubber roller several times. It's been 2 weeks free of jam now! I like it.