Recently someone posted about a machine that can not be upgraded to
15.6 because the media will not boot.

Link?

I am still working with Leap 15.4 and tried to install Leap 15.6.
Following the standard procedure (on July 29) I burnt the Offline-image with k3b and started the installation with option "Installation". The installation process stopped at the message 
"[ end Kernal Panic - not syncing: Attempted to kill init! exit code=0x00000004 ]", 
with the CAPS-lock LED flashing!
The same happened today (July 31), with a second (different) download of the Offline-image but using a USB-stick instead of a DVD. Also, I tried the network-image, with the same negative result

What is wrong, what should I do get Leap 15.6 installed?

Thanks in advance!
Franz