Well I still have a problem.
I have two Edisons on a Sparkfun base board, these two updated nicely.
The third is on an Arduino board, it's failed multiple times saying:
Uh-oh! Your Intel® Edison image did not update. This is likely because the Intel® Edison did not reconnect properly. You’ll need to download the newer firmware and manually update the Intel® Edison board. Detailed instructions available at https://communities.intel.com/docs/DOC-23192#jive_content_id_Step_4__Download_the_latest_image
I tried updating the manual way but it fails somehow.
I'm not very familiar with Linux so I can't determine why.
I also took the Edison and put it on the Sparkfun base and it still failed.
Maybe you can take a look here : https://software.intel.com/en-us/articles/flash-tool-lite-user-manual
this worked for me.
There is also the manual method : https://software.intel.com/en-us/flashing-firmware-on-your-intel-edison-board-windows