Build and Test continues to work on all my worlds that I've happened to try, except for one.
The world still works fine via VRChat normally using the Unity 6 beta, but trying to Build and Test the world results in the world loading, you appear in the world (at 0,0,0 it seems) for about half a second before being ejected from the world, given a VRC notice that you can't travel because you're offline, then being dropped in the error world.
The world in question is Squirrel Sounds but I can't attach the VRC log, Canny just keeps giving me a vague generic upload failure when I try (it's only 1.1MB).