A month ago my copier wouldn't duplex. Had a tech in and he found a small piece of plastic that was stuck in the bottom. When he removed it it worked fine. It happened again and he of course first looked to see if they was anything stuck in it again. He checked all of the connections and wiring which were fine except for one wire that he sautered. He said the only other thing it could be was the sensor. I just put it in and it still won't duplex. I have 700 36 page booklets that I have to have finished this Friday. Any suggestions would be greatly appreciated.