Solution:

Turn off the main power.

For details about how to turn off the main power, see "Turning Off/On the Power", Replacement Guide.

Open the front covers.

Pull down the lever C1.

Pull the drawer out completely until it stops.

Pull up and open the cover D3.

Clean the shading plate.

Using the dry cloth for cleaning the contact glass, wipe from the rear to front part to remove any fragments.

Clean the sheet-through exposure glasses.

Using the dry cloth for cleaning the contact glass, wipe from the rear to front part to remove any fragments.

Close the cover D3.

Push the left drawer slowly into the machine until it stops.

Pull up the lever C1.

Close the front covers.

Turn on the main power.

In the [Adjustment Settings for Operators] menu, execute 10: [Density Difference Printing: Across Feed].