Dust can accumulate on the media sensors. Use only a can of compressed air to clean the sensors.
Do NOT use an air compressor to remove dust. Compressors add moisture, fine grit, and lubricant which can contaminate your printer.
Clean the Movable Sensor’s window. (See image below for the location of the Movable Sensor—Black Mark and Lower Web/Gap.) Gently brush away dust or use a can of compressed air; if necessary, use a dry swab to brush away dust. If adhesives or other contaminants remain, use an alcohol-moistened swab to break it up.
Use a dry swab to remove any residue that may be left from the first cleaning.
Repeat the above steps as required until all residue and streaks are removed from the sensor.