I've had an interesting update journey. [tl:dr - it works out fine in the end]
I updated to 7.4.0beta when it appeared (spending alot of time at the computer with RM running !)
Today I saw Burkhard's post, and the 7.4.1 update..... and the instructions for the 'deadend' 7.4.0.
I put the new 7.4.1 update on my usb stick [sound of tense music] put it in the Kemper and initiated the update .........and it crashed. near the end. I rebooted the kemper, and I tried again [even more tense music].
This time it failed early in the update and had a new message along the lines of 'nand burn cannot find file', and something about the usb stick.
Rebooting this time..... went to the same screen. Again. And again. Oh. Dear.
I checked my usb stick.... and it was blank. My usb stick had clearly died during the updating process, and knackered the software/bios during the process.
So. Deep breath. Find new usb stick (borrowed from daughter), format it for fat32, put the last good update into the root directory. Put it into the Kemper, press the < page > and switch it on to tuner........ and it reloaded the bios........ when it was finished. it booted just fine, and hadn't lost any profiles. Winner, winner, chicken dinner.