Make sure the paper or media type you are printing on is within specification to avoid paper jams when 2-sided (duplex) printing.
Plain paper, Thin Paper, Recycled paper, Glossy Paper*1
60 to 105 g/m2 (16 to 28 lb)
Letter*4, Legal*2, *4, Folio*2, *3, *4, A4*4
*1: When you are using glossy paper, put only one sheet at a time in the MP tray to avoid a paper jam.
*2: Legal or Folio size paper are not available in some countries.
*3: Folio size is 215.9 x 330.2 mm (8.5 x 13 in.).
*4: Letter, Legal and Folio for USA/ Canada/ Latin America, and A4 for others.