OK, went here and extracted and overwrote these files:
.... and my server did not reboot.
I downloaded my Flash Backup from Unraid Connect, reformatted the USB Flash drive, and recopied everything.
My server booted, and everything seems to work.
Here are my diagnostics after re-installation and successful reboot: majors-diagnostics-20250325-0944.zip
I am still not sure the problem is solved, since I did these steps about 3 weeks ago...
EDIT 2025-04-02: It still works, problem seems to have went away, I marked this post as the solution. Thank you guys!
Thanks again for any hint!