I answer that, it must be said that it is possible for the pope to teach error in the exercise of his authentic magisterium, although the divine assistance granted to him in virtue of his supreme office prevents this from occurring frequently. (John P. Joy, Disputed Questions on Papal Infallibility [Os Justi Studies in Catholic Tradition 1; Lincoln, Nebr.: Os Justi Press, 2022], 11)
To put the matter briefly, a genuine internal assent to the truth of the teaching is generally expected, although there can be cases where it is legitimate to withhold this kind of assent for serious reasons. This is because we are dealing precisely with the non-infallible teachings of the Church, which by definition could be mistaken; at the same time, since the Church enjoys a special divine assistance in the exercise of her mission, even when the charism of infallibility is not involved, it would be wrong to conclude that the Church could be habitually mistaken at this level. (Ibid., 122; in this section, Joy is dealing with Amoris Laetitia)
On the 1910 “Oath Against Modernism”:
. . .if it were possible for such an oath to contain error in matters of faith, then it would be possible for the entire hierarchy of the Church to fall away from the true faith, for all Catholic bishops and priests were required to swear this oath for many years (1910-1967). But this is contrary to the indefectibility of the Church, according to the words of Christ: “The gates of hell shall not prevail against it” (Matt 1618). (John P. Joy, Disputed Questions on Papal Infallibility [Os Justi Studies in Catholic Tradition 1; Lincoln, Nebr.: Os Justi Press, 2022], 78)
On the recent change to the Catechism re. the death penalty:
If, therefore, the revised text of the Catechism regarding capital punishment were to be understood as asserting that the death penalty is intrinsically evil, then it would have to be rejected as false and heretical. If, however, the revised text of the Catechism should be understood, as some have argued, merely as a prudential judgment regarding the “admissibility” of using the death penalty in present contingent circumstances but without denying its intrinsic legitimacy, then it would still have to be criticized as badly expressed (male sonans) and savoring of heresy (sapiens haeresim). (John P. Joy, Disputed Questions on Papal Infallibility [Os Justi Studies in Catholic Tradition 1; Lincoln, Nebr.: Os Justi Press, 2022], 97-98)