Abort during coffee serving

HelloWe
have a Siemens eq900 s900 connect
After the last clean it always breaks off the coffee output after about 50ml.
Have now inserted a new brew group but has brought nothing.
Does anyone have advice?

my fully automatic coffee machine is now causing problems for the second time in 8 months. The machine freezes on startup and shows me the above error message.
I can only get out of the error display by unplugging and thus disconnecting the machine from power.
At the turn of the year I had the problem.... But patience helped... The machine simply sat in the kitchen for two weeks without power or water, just before I wanted to take the machine to MM, I did a test and lo and behold, the machine was running again.... Now I said to myself, ok, I will wait again... I am at four weeks and today I wanted to restart the machine, but this error message again.
I am grateful for any advice....

Thank you very much