There must be something wrong with the sensor. Generally, there will be no clean scraps of paper, or you can't see them in the fuser. You can only disassemble the machine. Disassembly steps: front cover, left and right side covers, manuscript table, back cover, and the cover under the manuscript table, so that you can see the fuser, see if there are scraps of paper, see if the sensor is in place, and clean the sensor by the way. ...