I think Māyājāla Sūtra precisely warns about this yet it seems to be ignored in EBT studies.
Maybe because it doesn’t neatly fit with the Sarvastivadin/Theravadin PoV of asserting real things. 
In this very way a noble disciple reflects thus: “to me, in whatever forms recognizable by the eye of the past, present and future there is no permanency or stability or eternity or thusness or non-not-thusness or non-other-thusness or reality or truth-ness or true existence or according-ness or non-perversion or non-distortedness."
The sutra outlines what would seem like a paradox of developping a higher knowing (adhicitta) what is, in fact, unknownability of any forms by signs.
Otherwise, there’s the paradoxical sounding description in SN 35.116, that I think serves as an analogy to the "gnosis of agnosticism ":
Bhikkhus, I say that the end of the world cannot be known, seen, or reached by travelling. Yet, bhikkhus, I also say that without reaching the end of the world there is no making an end to suffering.
We also have the message that Dharma should be used as a raft to be thrown away, used for an utility, not held as absolute.
We also refer to pedagogical devices rightly as conceptual (for example, taking care of yourself when there’s no self to be asserted) but we seem to conveniently imply that Buddha means something more concrete when he says to be understood.
So this feels as equally valid as someone saying “Buddha says cherish yourself, so self exists”.
But Buddha explicitly warns against any views in Chapter of Eights.
Sometimes EBT students refuse to hold the nuance of it, and reading the “No views” arguments as “No false views”. So when the suttas say explicitly “No views”, if you refuse to acknowledge it for what it says, then of course we can’t find suttas that warn against reifying knowledge or understanding. 
“Cleansed one has no formulated views” (Bhante Sujato) — you read this as “Cleansed one has no made up views that is incompatible with the world as it is (yathabhuta)” (which, I wouldn’t necessarily disagree with), when I hear that very yathabhuta to mean “There’s nothing that can be formulated about the world”.
This formulation seems paradoxical (perhaps, in a way it is) but more on that later.
For them not even the tiniest idea is formulated here
regarding what is seen, heard, or thought.
That brahmin does not grasp any view—
how could anyone in this world judge them?They don’t make things up or promote them,
and don’t subscribe to any of the doctrines.
The brahmin has no need to be led by precept or vow;
gone to the far shore, one such does not return. SNP 4.5
If ideas could be formulated about the truth of the world, why would the brahmin not formulate them rightly? If there could be any doctrine (dhamma) that could be true, why wouldn’t the brahmin subscribe to one (Dhammāpi tesaṁ na paṭicchitāse)?
The easiest explanation seems to me that the brahmin’s gnosis is beyond any attempts at formulation or doctrination.
Likewise, there are certainly a good deal of anti-realist and epistemically warning suttas that are often interpreted in a certain light.
The ilusion of SNP (“Nothing is real/what it seems”) and DHP, Phenasutta, to name a few. And a whole suite of suttas that talk about the limitations of knowledge and designations: Khandas arise neither by themselves, nor by any other, nor without a reason.
The problem isn’t that these suttas don’t exist — but they offer a radically challenging, truly ungrounding perspective, which can make it seem like rejecting the validity of the N8P. So they seem to be forced into certain narratives instead.
Of course, I could be argued to be doing the same thing. But I think what I lay out offers a logically coherent reading that is visible in this very life.
Oh, yes it’s not.
Hence Nāgārjuna warns against reifying emptiness as a theory to hold onto. Emptiness doesn’t refer to a stable ground, precisely!
Just because one can prove the incoherence of any formulated opinion, shouldn’t imply that a a new formulated opinion that “All formulated opinions are wrong” can be definitely asserted.
This is the epistemic humility I circle back to.
But it also doesn’t mean incoherence of specific arguments can’t be disproved, either! 
Likewise, bhante. May all beings benefit from our toil for the ease of their suffering!