Caffeo CI - No brewing water

Hello and good day,

a "brief" description of my problem
:Melitta Caffeo CI with about 9000 covers starts and cleans / rinses normally.
Then, for example espresso, the beans are ground, at the same time the machine heats up and some leakage water drips regularly from the drainage valve into the drip tray. Then the brewing unit is moved to the brewing position and the drainage valve closes.
The water pump starts and pumps some water into the coffee grounds, at the pump I "hear" a pressure buildup.... and as usual a short pause.

Now the pump should actually pump the water through the pressed and moistened coffee grounds into the cup... this step, however, is completely missing!
Rather, the brewing unit is immediately (without pause, without pump) moved to the home position and the pressurized water from the brewing unit is released through the drainage valve, which is now open again, and at the back over the coffee grounds
.

The machine moves to home position and grins maliciously.

I have already replaced the brewing unit, the drainage valve is also new.
I have tested the two microswitches under the drive cover, and the sensing lugs do not appear to be worn either.
The unit has already been reset to factory settings.
Milk froth and hot water are running fine as usual.

So... Perplexity here

The machine still has a limit switch that is operated from the flag of the brewing unit above.