Thank you. So, you and @t1000 both have firmware=0 in cat /proc/cmdline output (like me), and working option for you is fw_setenv flag_last_success 0....
.... Than I have run out of ideas on how to determine whether fw_setenv flag_last_success 0 or fw_setenv flag_last_success 1 is the working option for a particular RD23.
Remains a trial and error method only 