Vatican II says: The Bishops proclaim Christs doctrine infallibly whenever, even though dispersed through the world, they maintain the bond of communion among themselves and with the successor of Peter, authentically teach matters of faith and morals, and are in agreement on one position as definitively to be held.
Lumen Gentium § 25b.
Five conditions are therefore required:
Collegial action.
It is clear that the bishops must be involved in an exercise of teaching authority
as one body.
As judges.
The bishops must be free to express their own considered opinion.
In service of the faith of the whole Church.
The bishops must listen to the Word of God and the sensus fidelium.
Regarding faith and morals.
The teaching must concern matters relating to the object of faith.
In a teaching consciously imposed as definitive.
The bishops must want to impose the doctrine as definitely to be held.
I don't believe there has ever been a single infallible decision that would mee this criteria.
additionally, I need someone to define what "regarding faith and morals" truly encompasses, as It shifts around like a sapling in a windstorm when you try and pin it down.