Well, the question is, do the specific effects of damage look more like the effects that the "radio receiver" hypothesis would predict, or the ones that the "electronic brain" hypothesis would predict?
There is a big difference between an audio distortion and a semantic distortion. The radio-receiver hypothesis predicts that we can introduce audio distortion, but not that we can make the voice stop talking about vegetables. If we can only get the former sort of effect, then we are messing with a device that didn't understand vegetables in the first place; it did not contain any circuitry whose patterns correlated with facts about vegetables, only with radio and audio signal processing; the knowledge of vegetables was elsewhere. If we can get the latter sort of effect, then the device did have some patterns that had to do with vegetables.
No plot spoilers here, just wanted to flag a bit of poor reasoning that shows up in Chapter 39:
This is a surprisingly common fallacy. Just because X depends on Y, it doesn't follow that X depends on nothing but Y. A phenomenon may involve more than just its most obvious failure point.
To illustrate: Suppose I'm trapped in a box, and my only way to communicate with the outside world is via radio communication. Someone on the other end argues that I don't really exist -- "There's no person beyond the radio receiver, for if there was then there wouldn't be any such thing as damaged radios!" Pretty silly, huh? But people say this kind of thing in defense of physicalism all the time.
(N.B. This is not to defend the existence of souls. It's just to point out that this particular argument against them is invalid.)