The receiver seems to download the particular portion that is being updated (Main, Main ROM, Ether SBL, Ether IMG) and then does the updating.
When it is in the UpdateCheck OK screen, you have to wait for it to connect to the Denon servers again to download the next portion. Unplugging the unit is not recommended (as is mentioned prior to the start of the Update process).
The last update to the Ether IMG portion does take some time to download. Eventhough the unit usually says 1 min. remaining, it can take 10 or more minutes to complete that stage / portion of the update.
Having installers come back and look at it...if they can not do all the resets, reestablish net connect and then redo audyssey , then its off to the shop apparently.