Hi! Thank you so much, that was the correct answer. Sorry for the late reply, it took a while before I had time to give it a proper try. I had to use LVFS for 3.06, because indeed the USB one failed. I got pretty scared for a moment because I wondered if it had bricked my motherboard and if I should find a way to shut it down and try rebooting. Fortunately it all worked out. Did 3.19 with USB, and it was a much better process than with 3.06.
Cheers, and thanks for the help!
Leaving a link to the 3.06 post for posterity’s sake (in case anyone has the same questions and finds this thread):