OK, so this is not an uncontroversial claim, but I don’t care because it is not meant to be rude.
I have done an in depth study of the heresy of Jansenism. The primary heretical element in Jansenism was not the rigidity, not the opposition to the sacred heart and the tender devotion to the blessed virgin, but this- The denial that the Pope can make determinations in relation to dogmatic facts. What does that mean? Well, the Jansenists were reading a book by Cornelius Jansen called “Augustinus.” This book contained five propositions the Holy See claimed were heretical. The Jansenists said “Fine, we agree, they are heretical. BUT these propositions are not actually IN THIS BOOK, so we can go ahead and continue to read it as long as we agree with the condemnation of the DOCTRINE.” And for THIS they were condemned by the Holy See.
Now, to establish not only what is doctrinally false or true, but WHERE those doctrinal truths or falsehoods are located pertains to dogmatic FACTS. The Church is INFALLIBLE when it comes to establishing dogmatic facts. Some of these dogmatic facts are- the canonization of saints, the identification of her head (the Pope) and establishing what actions are or are not schismatic.
Now, what do the Feeneyites, Sedevacantists and SSPX all have in common? The denial of dogmatic facts. SSPX denies that when the Pope says, “Your act of consecration I take as an act of schism” that they need to abide by that judgment. To say nothing of the fact that they are now taking the position that canonizations are not infallible. The sedevacantist says “The Church can not identify her head,” even though the 19th century Theologians teach that to know whether a pope is a true pope or not is a matter of dogmatic fact. And the feeneyites refuse to accept the judgments of the Holy Office in regard to the necessity of water baptism.
The denial of these dogmatic facts seems to be a hallmark of all false traditionalist movements, as exemplified by the Jansenist and seen in these three groups in the present day.