I just tried to update to 3.19, but get exactly the same behavior.
Meanwhile, I was reviewing Getting started guide with a bare motherboard and suspect this has to do with the (lack of a) battery. I know the rtc is good, because the mainboard keeps time properly between shutdowns.
I just found the error.log on the boot USB, which says
Error 331: Full FW Update using same version is not allowed. Include -allowsv in command line to allow it.
I opened startup.nsh and appended the “-allowsv” flag to permit a retry.
fwupdlcl.efi -F fwupdate.bin -y -allowsv
Re-booted the USB and carefully watched it run through to 100% successfully updated. Again, it rebooted, but I’m still on 3.17. There’s no error.log file, so I presume it thinks it worked properly.