4035 send 1 2sided print job works fine send 2 or more it jams every time. First sheet comes out goes back in to do 2nd side when the second sheet comes out then goes back in to do 2nd side it only goes about half way back in then jams. If you do a 2 sided COPY it will run all day. I have replaced the entire exit section, the entire transport section and did a reset on the print system as well as reload drivers and get firmware up to latest version. Any suggestions??????

I was gonna mention amking sure the option is checked in the drivers box. I did forget that once and had the same problem on a 3035.

Other thing that has helped on this sort of weird problem is to replace that duplex drive clutch.

reloaded the print driver AGAIN and it seems to have started working.

Are you using the print drivers that are on the cd's that came with the machine? I downloaded from Kyocera.com the print drivers because the cd was missing from an 1815 trade in. The downloaded drivers updated the drivers for the XX35 series machines. Just another idea after having them update the drivers on my laptop that way in the last week.