Epson DFX-9000 Reference Manual page 116

When you switch between front and rear tractors, the paper jams
or the printer does not feed the paper back to the standby
position.
Cause
The printer may have reverse
fed too many pages.
You may be trying to switch
tractors when labels are
loaded in the printer.
When you switch between front and rear tractors, the printer
does not load paper onto the selected tractor.
Cause
The printer may be out of
paper.
116
Problem Solver
What to do
Use the tear off feature to tear off the
printed document or any excess paper
so that the printer needs to reverse feed
only one page. Then press the
Front/Rear button to switch tractors.
Labels jam when they are fed backward,
so always remove any labels loaded in
the printer before you switch tractors. To
remove labels loaded in the printer, tear
off the fresh supply below the tractor
and press the LF/FF Load button to eject
the remaining labels.
What to do
Load paper onto the tractor. The tractor
arrow on the Tractor Select indicator
should be green.