Automatic coffee maker interrupts brewing process

Hello Forum members,

after a few attempts I have not progressed with the repair of my coffee machine and now turn to you with the problem.

About the malfunction:
At certain intervals, the coffee machine stops the brewing process as soon as the brew group moves to the upper position and the pump should start to work. You can hear how pressure or water is released and the brew group then moves back to its starting position.
I'm also not really sure if the pump even starts or not just before it stops, in my opinion it does. The rinse function works every time, at least it has never happened that this was canceled.

The following attempts I have started:
- machine decalcified and cleaned, thereby the lime solution also in the system some time to persevere
- brewing unit dismantled and zerleget, thereby clean made, seals controlled and greased
- grinding degree increased and lowered
- grinder dismantled and made clean
- the microswitches on the drive on function controlled (with multimeter)
- flowmeter examined

I ask for your help and thank you in advance.

Greetings,
Phemantin

Had forgotten to mention that it is a Nivona CafeRomatica 758.

Checking the switches on the drive with the multimeter does nothing. Replace the two for the drive times. This is a known fault with the switches.

Is the switch above the drain valve activated when the brewing unit moves upwards?
If you are sure that the switches are ok. I always replace them in case of problems, to exclude the error.