I'm not sure if I would recognize or even discern any sign of heresy. I admire your perseverance.
It IS amazing to me that in spite of all the errant popes that served over the ages, no heresy has ever reared its ugly head long enough to become part of the Church teaching. If that's not proof of the guidance of the Holy Spirit I don't know what is.
Exactly. There have been some pretty bad Popes, but they have been preserved from error.
There were a couple of times when it looked like things might slip, but they didn’t. A bishop who was earlier on the Manichean side, along with the Byzantine Emperor, was elected Pope. But after the election, he dropped his Manichean position.
And I forget the details, but there was another Pope in the middle ages who was about to agree with some deviant Franciscan Friars on the nature of free will, but a group of philosophers from the University of Paris rushed to Rome and persuaded him not to go ahead with it. Evidently that was the closest any Pope came to heresy.
Selfishness and misbehavior, yes, as in the case of the Borgia Pope, Alexander VI—but God prevented even the worst of those Popes from promulgating heresy.
It really is miraculous.