The lint filters are soiled.
Clean the lint filters as follows:
Open the door.
Pull the upper lint filter forward to remove it.
Remove the lint (see arrows).
Remove the lint from the surface of all the lint filters and the perforated laundry deflector.
Turn the yellow knob on the lower lint filter in the direction of the arrow (until you hear it click).
Hold the knob and pull the lint filter forward to remove it.
Use a vacuum cleaner with a long crevice nozzle attached to remove any visible lint from the upper air flow openings.
Clean all lint filters with water:
Wipe the smooth plastic surfaces of the lint filters with a damp cloth to clean them.
Rinse the filter surfaces through under warm running water.
Shake the lint filters thoroughly and then dry them carefully.
Push the lower lint filter in completely and lock it with the yellow knob.
Push the upper lint filter in completely.
Close the door.