Every mature person who professes to be Catholic must have at least a rudimentary and manly ability to operate his rule of faith (ratio fidei) in order to discern what must be given the assent of faith, religious submission, pious assent, or plainly disbelieved. If Catholics don't have that, they're no better off than the followers of Martin Luther or John Calvin, etc., believing what they cannot determine to be more than doctrines or precepts of men.
In the case of the Second Vatican Council, judging it by the explicit rule given in the First Vatican Council (Dog. Const. on the Cath. Faith, Ch. 3, On Faith, #8; First Dog. Const. on the Church of Christ, Ch. 4, #9) and the Holy Father Paul VI's words, we know that the council was not an infallible one. This means that all those other councils which the Roman Pontiffs confirmed by their infallible magisterium supercede the Second Vatican Council in authority. This plainly means that if the Second Vatican Council contradicts, or is contrary to, those decrees made that the previous Ecumenical Councils coming from the chair of Peter, the Second Vatican Council errs.
Take for example and excerpt from Lumen Gentium, #11:
"Those who approach the sacrament of Penance obtain pardon from the mercy of God for the offence committed against Him and are at the same time reconciled with the Church, which they have wounded by their sins, and which by charity, example, and prayer seeks their conversion."
This is an absolute statement meaning one must merely approach, or come into the vicinity of, the sacrament to obtain pardon of God and reconciliation with the Church.
Compare that to what the Council of Trent taught in its Fourteenth Session:
"Contrition, which holds the first place amongst the aforesaid acts of the penitent, is a sorrow of mind, and a detestation for sin committed, with the purpose of not sinning for the future. This movement of contrition was at all times necessary for obtaining the pardon of sins....
"But, whereas all mortal sins, even those of thought, render men children of wrath, and enemies of God, it is necessary to seek also for the pardon of them all from God, with an open and modest confession. Wherefore, while the faithful of Christ are careful to confess all the sins which occur to their memory, they without doubt lay them all bare before the mercy of God to be pardoned: whereas they who act otherwise, and knowingly keep back certain sins, such set nothing before the divine bounty to be forgiven through the priest: for if the sick be ashamed to show his wound to the physician, his medical art cures not that which it knows not of.
"Finally, as regards satisfaction, - which as it is, of all the parts of penance, that which has been at all times recommended to the Christian people by our Fathers, so is it the one especially which in our age is, under the loftiest pretext of piety, impugned by those who have an appearance of godliness, but have denied the power thereof, - the Holy Synod declares, that it is wholly false, and alien from the Word of God, that the guilt is never forgiven by the Lord, without the whole punishment also being therewith pardoned. ... And it beseems the divine clemency, that sins be not in such wise pardoned us without any satisfaction, as that, taking occasion therefrom, thinking sins less grievous, we, offering as it were an insult and an outrage to the Holy Ghost, should fall into more grievous sins, treasuring up wrath against the Day of wrath."
The Council of Trent teaches us, in opposition to the Second Vatican Council, that it is not enough to approach or come near to the sacrament to obtain pardon and reconciliation: one must also be prepared to supply the parts of penance (i.e., the matter of the sacrament) contrition, confession and satisfaction, without which no pardon is given.
If the laity are not able to discern this, being unschooled in theology, then what hope do we have when priests contradict bishops who contradict popes who contradict themselves, etc.? How would we be able to discern authority with no standard by which to judge? If it's only a "because I said so" thing, then, why should we not all be protestants as it suits us?
Paul VI approved the Documents of VII. So although he made no formal pronouncements, he did speak on faith and morals in approving them. At the very least, he thereby confirmed that there was nothing in them that was against faith and morals.
So again, the Council made no new pronouncements; it changed nothing in either Dogma or Doctrines. It is, therefore, totally immaterial and unnecessary to even worry about infallibility or errors. There were no errors in faith or morals.