The problem is most likely with your fuser which is located in the rear of the printer. You may want to remove the fuser to inspect it for visible damage to determine whether it need to be replaced or not.
While looking at the back of the printer, pull the rear output door open. Push the door down to disengage the rear door stops (1). You will need a phillips head screwdriver to remove the two screws on each side of the rear cover. Lift the bottom of the cover first to disengage the alignment tabs at the top of the back cover, and then lift the cover away from the printer.
Remove the duplexer inlet guide by releasing two tabs (1) on the guide, and then sliding
the guide toward the back of the printer.
Disconnect two cables at the right, inside, of the device (callout 2), and then disconnect the fuser
power cable at the left side of the device (callout 3).
Remove three self-tapping screws (callout 4) and one grounding screw (callout 5).
Tilt the fuser slightly toward the back of the device, and then slide the fuser out of the back of the
device. Look at the two rollers inside the fuser and turn the gear on the side as you look at it. There may be something stuck inside the printer that is causing it to malfunction. If you see and damage on the fuser you can buy a new one from http://www.lbrty.com/
Good luck and I hope this helps!