And for completeness, I can confirm this also worked for me upgrading the Analog Four mkii from OS 1.40 to 1.40A. I used a USB cable rather than DIN MIDI and it was so fast I thought something hadn’t worked properly!
If anyone gets failures when upgrading, try using the --sysex-interval= option to something like 200 to 500 milliseconds (amidi --port=hw:1 --sysex-interval=200 --send=blah.syx). Failures happen when sending SysEx files too fast.