Check the following points to resolve the issue:

1. Wipe the windows of all four LED heads with a dry, soft lint-free cloth.
   > Click here to see how to clean the LED head.
    
2. Wipe the scanner glass strip with a dry lint free soft cloth.
    
3. Make sure foreign material such as a torn piece of paper, sticky notes, or dust is not inside the machine or around the toner cartridge and drum unit assemblies.