I didnt know what happened, but I knew that I had some problems in the last weeks which I thought I fixed. The rods where to dusty which resulted in the X-Axis skipping. I cleaned thhe rodes and sprayed some Teflon grease on thm, as usual. Maybe something got into the electronics box and the grease isnt as non-conductive as I thought?
So I opened the electronics box, unplugged all cables and checked the fuses. No fuses blown. I checked all important power-traces and all worked fine. I was worried that it really was the last blow for the printer and in my head I already thought which one to get next.
But then I noticed the real problem: On my PC, Home Assistant was open. The selected entity was the zigbee-plug, on which my printer is connected. My cat was sitting on my keyboard. He stepped on my keyboard, pressed the key combination to select the Zigbee Plug and turned off the plug, cutting power to the printer. The beep was the power-failure. The printer didnt turn back on again, because the Zigbee plug was still turned off.
No hurt feelings, but if you ever have a similar problem: check your cats.
Also, here is a picture from the villain:
The first 3D printing problem in history that needed a CAT scan to solve