Just in case anyone still has these issues I'm going to post how I found a way to resolve them. I had all the problems mentioned in the previous posts and more besides. The inability to apply OTA updates, the device would freeze after 5 seconds of inactivity, endless boot loops, failed recovery partitions etc etc etc.
I tried a butt load of different solutions but none worked for me. What did work is described below. Others have already mentioned that Advent has a stock rom recovery utility, however, even after flashing that my problems still remained. So I downloaded the Advent stock recovery util and documentation and modified it slightly to the latest Android release for the Tegra Note 7.
Do as follows:
1 - Go here
and download both the Advent Vega Tegra Note Factory Image (4.3) util and the documentation
2 - Extract the Advent Factory Image zip file (as described in the documentation) somewhere on your pc.
3 - Inside the extracted folder you'll see a bunch of files. The three files we're interested in are the "recovery.img", "system.img" and "boot.img". Select all three and delete them.
4 - Now download the Tegra Super Tool utility here
. At the time of this post the latest version is 2.5.
5 - Extract the downloaded Supertool to a new folder on your pc.
6 - Inside the extracted folder there are another bunch of files. Again, we're only interested in three of them. You're going to rename three of the files and use them to replace the three files you deleted earlier. At present their names are "4.4.2-2.5recovery.img", "4.4.2-2.5boot.img" and "4.4.2-2.5system.img.ext4". The filenames will obviously change as time goes by, but a little common sense goes a long way at this stage. So "4.4.2-2.5recovery.img" is renamed to "recovery.img", " 4.4.2-2.5boot.img" is renamed to "boot.img" and "4.4.2-2.5system.img.ext4" is renamed to "system.img". Once you've renamed them, copy them into the folder for the Advent Vega Tegra Note Factory Image which you extracted in step 2.
7 - Now go and read the documentation for the Advent Vega Tegra Note Factory Image util. Just take your time and follow it to the letter. It'll tell you how to put your Tegra Note 7 into it's APX mode, install windows drivers for it and begin the recovery of your device. It's mostly an automated procedure and fairly simple to follow as long as you follow the documentation.
This method brought my Tegra Note 7 back when it had several of the problems mentioned earlier in this thread, all at the same time.
Hope it helps someone.