the current is reversibly interrupted internally

Hello experts,
when preparing cappuccinos, the power has recently been interrupted internally after the milk foam preparation (=when it wants to brew), the machine stops and the display is dark. After switching off at the power switch and waiting approx. 1 minute, it works again, I then pour a clean coffee into the cup and that's it.
On the advice of a very knowledgeable Nivona technician, I descaled it "heavily" (300 ml descaler to 200 ml water) and cleaned it, after which it made normal cappuccino and all other coffees again. Only with a large cappuccino (350 ml, set under "my coffee") is the power interrupted internally again after the milk foam preparation (=when it wants to brew), the machine stops and the display is dark. After switching off at the power switch and waiting approx. 1 minute, it works again, I then pour a "coffee lungo" into the cup and that's it.
Which element reversibly interrupts the power supply here, and why?
What else can I do about it?
Many thanks for your support!
With sunny greetings
Stefan