Ex Cathedra -- are there other Christian groups besides Catholicism that use a similar tactic? We're all familiar with the concept of the papal infallibility and how the pope is considered infallible only when speaking ex cathedra, which creates a lot of wiggle room since there is really no clear criteria for determining when he's speaking ex cathedra (my opinion, but see Can we tell when the Roman pontiff is speaking &quot;EX CATHEDRA&quot;? and its many duplicates), and that he's sitting down apparently doesn't mean anything even though that's the literal translation (from a chair). This ex cathedra thing creates a sort of "Nope, he didn't say Simon says, so that doesn't count" effect.  Anyway my question is not at all about that.  My question is are there any other Christian groups, sects, denominations, that use a similar tactic to prevent their leader from the appearance of having taught false doctrine?  For example: Might Mormons use the same kind of argument to prevent the appearance that their prophets contradict each other infallibly?
Mormons do, in fact, have a somewhat similar doctrine, but more limited in scope: that the President of the Church cannot lead the church into apostasy with false doctrine.


  The Lord will never permit me or any other man who stands as President of this Church to lead you astray. It is not in the programme. It is not in the mind of God. If I were to attempt that, the Lord would remove me out of my place, and so He will any other man who attempts to lead the children of men astray from the oracles of God and from their duty.
  
  -- President Wilford Woodruff, October 1890 (emphasis added)