@David-TP

Your reply of " If all the TVs are wirelessly connected to Deco, or connected to other satellite Deco units(Deco 2+Deco 3) via Ethernet cable in the layout, they will still work properly. "
 

This seems to indicate that I should be able to access my media via any wifi connected device but I cannot do that.

As I mentioned " Whenever the internet connection goes down none of my TVs (with nVidia Shields and connected HDDs) can access my stored media via wifi. "

According to the other thread titled "WAN/LAN Autosensing" ethernet connected devices will not be accessible on the LAN when the internet connection drops.

What I am trying to find out is the WAN/LAN Autosensing 'feature' that pevents ethernet connected devices from connecting across the LAN also stopping wifi connected devices from functioning too.

Not sure how to attach images here yet but this is my current layout  (dotted lines indicate wifi and solid lines are hardwired) -

LAN layout

I may have worked out the image posting....

In summary..... When the internet connection drops none of my devices are able to connect to each other at all.

  @David-TP 

So, do I understand you correctly that all of my wifi devices should be able to connect across the LAN?

You say " If all the TVs are wirelessly connected to Deco, or connected to other satellite Deco units(Deco 2+Deco 3) via Ethernet cable in the layout, they will still work properly. "

But none of my devices are accessible anywhere on my LAN every time I lose internet connection..

If you are correct then I must have something configured incorrectly. Can you suggest how I resolve this?

If you are incorrect then this hardware is basically useless the way TP-Link have it set up.

  @David-TP 

Thank you for getting back to me - I assume the email from support is from you so I will reply to that with my Deco App email address as requested.

" 1. When the internet went down if you check the Deco APP device list(Please still connect the smartphone to the Wi-Fi of Deco even though there is no internet), will you see these two Shield TVs get IP addresses from Deco? "

Both nVidia Shields still show the same IP addresses even when not connected to the internet.

"

2. You mentioned that " "Whenever the internet connection goes down. none of my TVs (with nVidia Shields and connected HDDs) can access my stored media via Wi-Fi",

Do you actually mean neither Shield TVs are unable to access the USB HDDs that are connected to each other, such as TV1 can not access the USB HDD that is connected to the TV2 and vice versa?

--If yes, would there be any error message and can I have a picture?"

This is precisely what occurs - each unit can access files on the drive attached directly to it but neither can access files attached to the other unit.

The only error message that appears is "Playback Failed. One or more items failed to play. Check the log for more information about this message."

This is when I use Kodi to attempt to watch a movie or TV episode from the HDD via the nVidia Shield. The log only shows "Video Library Scanner. Failed to scan tvshow."