[Shield Android TV Q&A, Help & Troubleshooting] nadia p.:
HISTORY

My device: Nvidia Shield TV 2017 (16GB) Remote Only, P2894 (Darcy) | Android Oreo 8.0.0 | Nvidia 7.1.0 (developer) | patched boot.img using Magisk Manager 6.1.0 & Magisk 18.0 | TWRP 3.2.3.0 (foster)

OBJECTIVE

The main reason for installing TWRP was so I could backup the entire system in case Nvidia Experience was accidentally updated or some other app(s) and I could restore the backup and continue from there.

DISCLAIMER

Prior to flashing TWRP to my device I had originally gone through these steps.

New device (factory OS) was updated to 7.2.0 and later 7.2.1 by agreeing to on-line updates. This broke many apps and rendered my device useless.

In trying to resolve this I download and overwrote the existing 7.2.1 installation with 6.3.0 developer OS after unlocking the bootloader. Little did I know at the time that following this method would work however once connected to the internet and signing into Google Play would then force the device to be updated again back to 7.2.1 (at that time).

Later I discovered ACiDxCHRiST's [GUIDE] Root NVIDIA SHIELD Experience Upgrade v7.2 with Magisk v18.0 and with his assistance was able to download and install 7.1.0 developer OS successfully.

After getting everything working perfectly all I wanted to do was to back up the device and later be able to recover that state if required. Seems easy and logical right? Not really.

[SUCCESS] Installed TWRP 3.2.3.0 (flash method)

My device is connected to a Windows 10 PC using a USB-A cable (male to male). The device is booted to the Nvidia Home Screen and I'm logged into the PC as Administrator. The device has a USB hub plugged into the USB port closest to the HDMI port. The USB hub has a USB keyboard and USB mouse plugged into it. From the PC, I launch a Command Prompt window as Administrator and execute the following commands.

adb devices

List of devices attached

############ device

adb reboot bootloader

fastboot devices

############ fastboot

fastboot flash recovery twrp-3.2.3-0-foster.img

target reported max download size of 67108864 bytes

sending 'recovery' (17278 KB)...

OKAY [ 0.437s]

writing 'recovery'...

OKAY [ 1.016s]

finished. total time: 1.453s

fastboot reboot

rebooting...

finished. total time: 0.016s

The device boots to the Nvidia Home screen

The installation appears to be a success.

NOTE: The USB-A cable remained connected to the device and PC this entire time.​

[SUCCESS] Boot into TWRP Recovery Mode

adb devices

List of devices attached

############ device

adb reboot recovery

adb devices

List of devices attached

############ recovery

The device boots to the Team Win screen displayed on your tv/monitor (less than 4k).

Using the USB mouse swipe (left to right) >>> Swipe to Allow Modifications

Click Backup

<place holder for image>

The only change (from the default settings) based on the recommendation HERE was I checked [x] Cache

Using the USB mouse swipe (left to right) >>> Swipe to Backup

The backup starts.... the progress bar completes... I look for a way to save a log file but I don't see any. When finished I use the < "back arrow" button toward the bottom of the screen to navigate to the main menu, then press Reboot.

The backup appears to be a success.

NOTE: The USB-A cable remained connected to the device and PC this entire time. The USB hub remained connected as well and had full use of the USB keyboard and USB mouse.​

[FAILURE] Reboot to Nvida Home screen

The device boots...

ORANGE: Warning screen for UNLOCKED devices will appear for 2 seconds, then goes away.

The Nvidia Logo will appear for 3 seconds, then goes away.

RED (eio): Warning screen for dm-verity corruption will appear for 10 seconds, then goes away.

RED (eio): Warning screen for dm-verity corruption will appear a second time for 8 seconds, then goes away.

Afterwards nothing but a black screen. There's no way to control it with the remote, keyboard or mouse. All access through ADB is also disabled.

The only way to do anything from this point is to disconnect the power.
​

[NEXT STEPS?] What can we learn from this?

What's the root cause or reason that lead this device to become corrupt or the system to believe it's corrupt?

What steps does a user have to perform to verify and understand if they can or cannot install (flash) TWRP onto their devices and use it successfully to backup and restore their entire system?

What's required to get back to a working device again?

What is the correct process and procedures that should be followed in the future?

work in progress... to be updated...