I have adjusted the ADF right bracket for the skew, machine also skews when you scan an image and bring it up on the desktop. There are some little black spacers if that what they are called, mountes on the scanner /lamp ass'y that rides on the rails. Trying to see how many there should be , the book is not specific

Does it only skew thru the doc feeder or also on the glass? If only doc feeder, polish the glass with antistatic spray. Are the hinges good or does the doc feeder fall down? Maybe replace hinges?