Dust can accumulate on the media sensors. Use only a can of compressed air to clean the sensors.
This image shows the location of the Movable Sensor for black mark and lower web/gap media.
Clean the Movable Sensor’s window. 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.
Do NOT use an air compressor to remove dust from the sensor or the inside of the printer. Compressors tend to add moisture, fine grit, and lubricant which can contaminate your printer components and interior.
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.