1. Ah I meant, try manually calling Read() or Rebuild(true) when updating text in your code! Also I forgot to ask, is this happening only in editor, or does it still happen in a build? There's unique behaviour for changing the rectTransform in the editor that causes a rebuild... but it shouldn't happen when the game is playing, which would be the bug. I'll take a look at it soon!
2. Ok I'm glad the ultra shader works here! It's eventually going to replace the other shaders anyway, so I'll accept it as a fix.