After a paper jam was cleared in the duplexer it will no longeraccept and flip the sheet for printing on back side. Examining the duplexer I see that the black exposed gear that should engage with the white gear in the body of the printer simply spins without turning the duplexer’s feed wheels. Anyone have any experience on how to open the side of the duplexer to see what has slipped? Or have a schematic of the duplexer?