To the degree we teach false doctrine we are in sin. YAH is very patient (for the most part) and desires that men submit to the Holy Spirit as he guides us into more truth. But like you say he doesnt seem to give "assurance" that we can in the end be saved if our doctrine is false.
Of course SOME of them will say all that matters is
Acts 2:38 and Oneness. About anything else and they gives themselves a pass!