Yeah, the more I look at it, the more obvious it is that Temptation is the OS Problem. Remember Pippin and how he’s tempted to sneak a look at the Palantir (Saruman’s one, which Gandalf had carefully wrapped up) when Gandalf is asleep? Massive conflict from that – not just for Pippin but for Gandalf and even Sauron (who ends up believing Saruman has the Ring).
Not to mention, Gandalf describes that Saruman’s corruption likely came from his temptation to use the Palantir to look on Barad-Dur:
But there is nothing that Sauron cannot turn to evil uses. Alas for Saruman! It was his downfall, as I now
perceive. Perilous to us all are the devices of an art deeper than we possess ourselves. … Very useful, no doubt, that was to Saruman; yet it seems that he was not content. Further and further abroad he gazed, until he cast his gaze upon Barad-dur. Then he was caught!
You can see the Symptom of Disbelief there too, in how Gandalf implies Saruman was caught because he ignored (disbelieved) the danger of such powerful magic.
You can also see Disbelief → Faith, along with a hint of the Conscience solution, in this exchange between Pippin and Gandalf afterwards:
‘I wish I had known all this before,’ said Pippin. ‘I had no notion of what I was doing.’
‘Oh yes, you had,’ said Gandalf. ‘You knew you were behaving wrongly and foolishly; and you told yourself so, though you did not listen. I did not tell you all this before, because it is only by musing on all that has happened that I have at last understood, even as we ride together. But if I had spoken sooner, it would not have lessened your desire, or made it easier to resist. On the contrary! No, the burned hand teaches best. After that advice about fire goes to the heart.’
‘It does,’ said Pippin. ‘If all the seven stones were laid out before me now, I should shut my eyes and put my hands in my pockets.’
‘Good!’ said Gandalf. ‘That is what I hoped.’
Gandalf is like, “if I’d told you, you would have just ignored / disbelieved my warnings anyway. You needed to be burned by the fire to believe in the danger.”
On the Disbelief Crucial Element, I’ve been wondering if it’s something like, refusing to accept that Hobbits are too small / weak to get the job done, or something like that? I could see that as being pretty close to the message of the story…