Melitta Caffeo CI too little coffee

Hello all,

since 3 days comes with my coffee machine unfortunately too little coffee in the cup.
The coffee jet is very thin and the machine does relatively difficult to pump the coffee through.
Had thus suspected the flowmeter. After replace against a new there was unfortunately no improvement.
When making coffee I have also already checked the drainage valve and the grinder, no water leakage, only 2 to 3 drops of water come out of the drainage valve.
Coffee maker already descaled several times, also with warm water and quite a lot of descaler.
Brew group soaked in water and then blown through the screens with compressor.

I know unfortunately no further, has anyone of you an idea? I am in despair.

Many thanks for your help!

What did you use to decalcify?

Several times with coffee machine descaler and then 2 more times with vinegar essence.
Have also let it soak for half a day.

Ws you need to replace the overflow valve