Firmware 13.2.0 - DOS 2.2.6 for Expert Pro - Release note

[Damon]

Have just updated both units in my 440 Pro CI configuration. A word of caution or just confirmation from those who have upgraded dual units.
...
To solve, I had to copy the files completely again to the SD card from my computer. Then placing it in the second unit finally kicks off the upgrade process. There's a file that gets erased, apparently, after you use the SD card once to upgrade a unit. (I believe it's fw.txt but I could be mistaken.) So the list of files required for the upgrade is incomplete after using it once already for an upgrade.

Yes, that is correct. The config files on the card are changed, with one file deleted, as you note. I don't understand any of the config stuff, but it has always been this way. The general advice has been to be thorough in deleting all the files on the card before using a new config file. For some it works to just empty the trash/ recycle bin (it works for me) and others have to reformat the card to get it completely clean. An oddity, but that procedure is part of the process. I tend to go years between config changes so I usually forget something.