I don't know what happens, but the pluscart duo updates were not asking for an update over the wi-fi, only the pluscart version, this older one asked for the update to FW 2.3. pluscart duo I tried to install via SD card, but the same thing happened.
Probably the various attempts that you saw to update were mine, I tried on several boards that I had here, but there were 2 computers with problems, but only on the traditional pluscart that asked for an update.