Trouble live-booting S905 already running LibreElec

MY LIBREELEC
I recently converted my Nexbox S905 1G/8G from Android to LibreElec 7.03.12a and manually upgraded it to LibreElec 7.03.12c via SSH. In summary; a succesful toothpick install from a USB drive - and a great improvement in daily use of Kodi, now that I'm running LibreElec.

THE PROBLEM
I cannot get my NexBox with LibreElec to live boot from my USB drive anymore. Neither the old/original USB stick which worked perfectly for installing LibreElec 7, nor the other USB with LibreElec 8. Nothing has changed (same USB port on the NexBox, USB drive, image file and dtb - kept the USB as-it-was), except I'm now running LibreElec.

GOAL
Run the beta 2 with Kodi RC3 on a live USB. I am familiar with the manual upgrade procedure, but I am hesitant to upgrade directly to LibreElec 8 and would like to test LibreElec 8 before installing it permanently.

ALREADY TRIED
I dd'ed the unpacked image file and copied the dtb.img. So, I'm good to go. Pop in the USB, unplug the power adapter, hold the reset button, replug the power adapter. NexBox a95x logo - forever. Try the other USB port. Try the first USB port, again. Retry ad nauseam. Normal boot via NAND works fine. Then I came here for assistance.

I need some advice and helpful pointers on booting LibreElec 8 beta 2 from USB on a S905 system (NexBox a95x) already running LibreElec 7.

Thanks in advance.

Quote from her

Have you tried to boot without the recovery button pressed? That isn't necessary after the first time; if you want to boot from USB just insert and power on.

Before installing LibreElec, when running live-boot on top of Android, that worked nicely. But whether I hold the reset button or not, the boot from USB is stuck in the process, since I installed LibreElec to NAND. It simply does not progress from the NexBox logo to the LibreElec logo and bit into Kodi.

Thanks for joining in, though. I'm baffled by this.