I guess the St. Pius X taught material heresy in his catechism:
29 Q. But if a man through no fault of his own is outside the Church, can he be saved?
A. If he is outside the Church through no fault of his, that is, if he is in good faith, and if he has received Baptism, or at least has the implicit desire of Baptism; and if, moreover, he sincerely seeks the truth and does God’s will as best he can such a man is indeed separated from the body of the Church, but is united to the soul of the Church and consequently is on the way of salvation
And St. Alphonsus Liguori taught material heresy when quoting the materially heretical Council of Trent:
St. Alphonsus Liguori (1691-1787) Moral Theology - (Bk. 6): “But baptism of desire is perfect conversion to God by contrition or love of God above all things accompanied by an explicit or implicit desire for true Baptism of water, the place of which it takes as to the remission of guilt, but not as to the impression of the [baptismal] character or as to the removal of all debt of punishment. It is called ‘of wind’ ‘flaminis’] because it takes place by the impulse of the Holy Ghost Who is called a wind ‘flamen’]. Now it is de fide that men are also saved by Baptism of desire, by virtue of the Canon ‘Apostolicam De Presbytero Non Baptizato’ and the Council of Trent, Session 6, Chapter 4, where it is said that no one can be saved *‘without the laver of regeneration or the desire for it.’” *
Or maybe they were completely orthodox.