Regardless of which avatar you attempt to load (only personal uploaded should work) it will instantly reject the request to download and refuse to load from cache if already in cache.
Tried clearing cache and downloading from regular live client (which works fine in live).
Optional cleaning for test
  1. Clear content cache in live client.
  2. Restart live client and allow avatars you've uploaded to load.
Steps
  1. Launch Build & Test by any means into a test world.
  2. Instantly shows error robot and presents the attached error for any attempts at loading avatars.