I was thinking of basically using an optical encoder on the "big"? It seems like that is the one that takes the hammering, especially as it is also a switch..?!
Is the actual "knob" part of the encoder well supported? ie: if you try and bend the shaft from side to side, does it move (much)..?
Maybe replacing the knob itself with a type that rotates within the panel hole, rather than hanging off the shaft, and replacing the 89p encoder with a new one, would offer a much longer-term solution?
As I say, I don't actually have an Origin (yet!)..so I don't know the full story.....
But I'm already drafting up something in Solidworks as a preliminary solution, maybe...... ;-)