The brew unit has not been sufficiently cleaned.
The brew unit must be cleaned manually in addition to the automatic cleaning. A cleaning tablet may be required to degrease the brew unit even if the cleaning cartridge is fitted.
Proceed as follows:
Open the appliance door.
Remove the water container.
Press the button on the bottom of the brew unit handle (1).
Whilst doing so, turn the handle forwards (2).
Pull the brew unit sideways first (1).
Then slide it out forwards (2).
Tilt the brew unit forwards (3).
Rub away any coffee residues from the filters. One filter is located in the funnel. The other filter can be found to the left of the funnel.
Dry the funnel to prevent ground coffee sticking to it the next time a coffee is made.
Clean the inside of the coffee machine.
Use a vacuum cleaner to remove dry coffee residues.
Clean the brew unit niche with a damp, clean sponge cloth.