Actor images not showing on Android TV client

[br441]

I have a script that grabs metadata for UFC events and saves them to .nfo files to be used with XBMCnfoMoviesImporter. The actor images are stored on a public-facing HTTP server. In the Plex library settings, "actor thumb location" is set to "link". The .nfo files have thumb tags for each actor's image...

 <movie>
   <actor>
     <name>Stephen Thompson</name>
     <role>Welterweight Red</role>
     <order>0</order>
     <thumb>http://127.0.0.1:8080/global//stephen_thompson_left.png</thumb>
   </actor>
   <actor>
     <name>Joaquin Buckley</name>
     <role>Welterweight Blue</role>
     <order>1</order>
     <thumb>http://127.0.0.1:8080/global//joaquin_buckley_right.png</thumb>
   </actor>
   <actor>
     <name>Marina Rodriguez</name>
     <role>Women's Strawweight Red</role>
     <order>2</order>
     <thumb>http://127.0.0.1:8080/global//marina_rodriguez_left.png</thumb>
   </actor>
   ...
 </movie>

The actor images are visible on most devices (regardless of what network they're connected to), except on Android TV devices...

Web:

Desktop:

iOS:

Android TV:

And that happens regardless of whether or not I'm connected to same network as my server. I tried fiddling with different settings on the Plex client, as well as on the server to no effect. The Android TV device is able to connect directly to the server so that's not a possible reason. Also the firewall on the server is configured correctly and every port that Plex uses is allowed.