We should certainly try to understand the terms.

Pertinacity is one of the most incorrectly used terms.  Let's understand it by contrast.  Priest utters a heresy.  You point it out and he says it was a slip of the tongue.  Not petinacious.  You point it out, he looks it up, and he says, "oh, my bad ..." and retracts the view.  Not pertinacious.

Those are the types of things that pertinacity rules out, so someone doesn't lose membership for merely uttering a heresy.

Now, pertinacity does not require someone to consciously think, "I know that the Church teaches this and that it's heretical to deny it, and I deny it anyway."  That degree of conscious and deliberate rejection of dogma is not required, and there has been an attempt by R&R to turn pertinacity into some phenomenon that can only be discerned in the internal forum.

It suffices for petinacity that someone repeatedly make the assertion (so not a slip of the tongue or simple mistake) and appear to be very strongly in favor of it, i.e. for them to adhere to it.

Bergoglio, for instance, and actually all the other V2 papal claimants as well, teach the heresy that there can be salvation outside the Church, that the Old Covenant continues in force and is salvific for the Jews (the heresy Father Kramer points out) ... and they're certainly PERTINACIOUS about it.  They say it over and over again and teach it, and they're clearly adhering to it as something they strongly believe in.  That suffices for pertinacity.  Period.  There's no requirement to discern the internal forum, nor is that ordinarily possible.