This thread has evolved into a wall of text that, from a quick glance, contains a lot of wild guesses and incorrect assumptions.
@librem5 it appears that your device gets stuck at some point while trying to boot from USB (which is a prerequisite for both flashing and launching Jumpdrive). This can either mean issues with USB communication (on either host or device side) or outright broken hardware that can’t even successfully boot into the bootloader. Please contact support.