A brief update, I’ve just discovered that the same error occurs with the plugin editor too.
They don’t… they do on most themes, but on this one they don’t.
Gridlock is a really nice theme that you can see working here.
I came here to ask a question about the same theme, but I should be able to use the answer to this as a work-around… unless I could get away with hijacking this topic when it’s done with?