I can se that the thermistor works because it changes values in the display when touching the thermistor-end.

Good information. You can probably remove thermistor from possible cause, but to be sure, you can tape the thermistor to your heat bed, and heat to a high temp, make sure that the “nozzle” temp is close to the bed temp

What is the behavior when you hear the nozzle? Does it immediately give error, or does it take some time? If it takes some time, is the temp changing on the nozzle at all, or it stays the same until error?