Question

Hello Rabbi,
In the passage in Zevachim 16b, Rava proposes a problematic a fortiori inference, and Rava bar Ahilai attacks it (bringing it to absurdity?) with three opposite a fortiori inferences and concludes that “rather, one can refute it this way and one can refute it that way; let each one remain in its place.”
It is not clear whether we are dealing here with contradictory a fortiori inferences which, due to lack of knowledge, neutralize them all, or whether this is some sort of positive mode of resolution, and if so, what it is.
On the face of it, a practical solution to not knowing which a fortiori inference is correct might perhaps have been to treat it as a Torah-level doubt and rule stringently, but that is not the solution the Talmud suggests.
From Rashi it seems that the absurdity leads to some conclusion against Rava: “if regarding something in which the verses did not distinguish, you come to distinguish by means of an a fortiori inference…” or “it turns out that he is removed from all of them, and you will not know what to derive; rather, do not distinguish where the verses did not explain it to you…”
I would appreciate it if the Rabbi could shed some light, in his opinion, on whether there is here a dispute about the very ability to use an a fortiori inference in certain cases (with the absurdity serving only as proof of that), and if so, what is the case in which one should not use an a fortiori inference.
Thank you!