“A mistake made true”

I don’t know if it’s common to think this way, but there is a popular opinion that when there are disputes in laws (Tannaim, recent Amoraim or whatever), then the ruling itself turns the opinion itself into truth (what God wanted or intended). In other words, there is really no possibility that we are not doing God’s will because as long as we discussed things and some decision was made, then it is God’s will. It sounds a bit strange to me that there is no truth that God wanted us to do, but I can also understand this statement, because after all, we don’t have Urim and Tomit that we can ask and know for sure the answer. Does the rabbi think that there is a matter of the ruling itself turning the decision into God’s will or is there a situation where mainstream halakhah sometimes sins and is not aware of it? And if we do sin (because in your opinion there is one truth and we don’t know for sure what it is), then where do you learn this from and what proofs and justifications are there for this? Thank you very much.