This is one of those things that seems to blow right past folks who see the Church’s teachings divided into two parts: dogmatic definitions and everything else.

Papal infallibility, declared at Vatican I, was reaffirmed in “Lumen Gentium", which made other crucial points.

Infallibility also includes solemn teaching acts made jointly by the pope and bishops convened in an ecumenical council. Infallibility of the "ordinary magisterium" also includes the teaching of bishops in union with the Holy Father in "ordinary" acts of teaching outside an ecumenical council.

"Taken individually," says Section 25 of Lumen Gentium, bishops "do not enjoy the privilege of infallibility." Yet, "when, even though dispersed throughout the world but preserving for all that amongst themselves and with Peter's successor [the pope] the bond of communion, in their  authoritative teaching concerning matters of faith and morals, they [the bishops] are in agreement that a particular teaching is to be held ...".