I see, but the "to it" is what's grammatically incorrect.

It is correct to write: there is a "there" there. It would also be correct to write: there is a "there" to it. But it is grammatically incorrect to write: there is a "there" there to it.

Eh, maybe? But English grammar is consensus based. This is arguably bad grammar because people not knowing the cliché of "there there" had trouble understanding the intent, not because it's "wrong" under some hard citeable rules.

Moreover I think you could argue the author is using the phrase as an abstract noun. Consider:

That there's a solidity to it.

That there's a "there" there to it.

The first turns naturally to my ear; the second is a bit forced but works IMO.

I see, thanks.