Find defect after failed BIOS update

[EliteBook845G7]

My EliteBook 845 G7 with AMD processor and HP Sure Start (product number 2Z9T0EC) got broken during a BIOS update (sp152637.exe) which I started with closed lid via the USB-C docking station G5 where external keyboard, mouse, screens, power supply, headset and LAN are connected. When after the first reboot, a white screen with black text appeared, I switched to a tower PC to continue working on a different PC during the BIOS update. As usual, the notebook's fan was running fast during the BIOS update, but that did not stop, and when I wanted to check the progress, there was no video signal anymore, and when I opened the lid, the screen remained black. After 1½ hours, I kept the power button pressed to stop the notebook, but when I switched the notebook on again, it was the same: The screen remains black (I cannot even see a backlight), and there is no video signal at the HDMI connector or via the USB-C docking station. I repeated that several times. There is no beep or blinking sequence when I switch the notebook on. The keyboard illumination switches off after about 10 seconds. The fan increases its speed slowly to maximum, and the notebook gets hot. I can stop the notebook only by keeping the power button pressed for about 5 seconds. (This starting and stopping does not only work with the built-in power button, but also with the power button of the docking station when I connect it.) After the forced power off, next to the power connector, an LED rapidly switches about 11 times from white to orange and back. What does this mean? This pattern is not covered in https://support.hp.com/us-en/document/ish_1997719-1528356-16.

I reset the notebook by keeping the power button pressed for about 15 seconds (with external power supply disconnected). Afterwards, the caps lock LED was on for about 7 seconds, and as usual, after releasing the power button, the LED next to the power connector was blinking as described. I tried also unsuccessfully pressing Windows+b during switching on (with external power supply connected) as well as powering on with a USB recovery memory stick that I created although this is not expected to work with HP Sure Start.

Disconnecting both batteries for one night did not change anything either. I removed the memory module, then the notebook beeped when I powered it on, I reinserted it in a different and eventually the same slot, but there was still not even an observable backlight or a video signal at the connector. I also let the notebook run without external power supply until it stopped with an empty battery.

When searching for help, I read in the user manual that the notebook should not be connected to the docking station during BIOS update – a piece of information unfortunately not provided in the instructions of the BIOS update program. What hardware damage may it cause, what component gets broken? It seems that it is not just a misconfiguration of the BIOS because that should result in a blinking sequence already when powering the notebook on and should automatically repair itself.

Thank you in advance for an explanation of

• the fast about 11 times blinking of the LED next to the power connector from white to orange and back or

• what hardware component gets broken when running a BIOS update with closed lid via a docking station!

[Stefan_R1]

Thanks for also opening this thread here:
Withdrawal of HP BIOS and System Firmware (S77) Version 01.1... - HP Support Community - 9088473

where the first reply directs to three very active threads on the very same issue (although with different models) where the BIOS (01.17.00) happened to break the self-repair mechanism.