Back to the body octave system.
The material in guide blocks at top. Remove for now.
Review alignment of octave key arm (the one with pad) and the clearance to touch arm tuning fork. It looks too close.
The roller needs to turn freely. The bottom of the G hold down finger could benefit from a veneer of leather or cork. As is it will be noisy.
This could be straighter.
Once straight I would place a bit of cork under the arm. Not on the body. This I would experiment with different thickness.
It will back the octave fork off the neck maybe enough ?
This should increase the pressure on pad as the fulcrum points I think favorably.
At the same time the touch lowers to being more level with thumb rest.
Make sure the top of body octave vent is nice and smooth. No impression into pad as it looks as though it has some sliding action to the movement.
Shrink tubing on the guide fork could be ok. Just a partial band at travel distance area, both sides.
Neck on.
The octave lever has clearance to halo.
Press the octave touch, the crook octave key should open 2-3mm.
Press G, the neck octave key spring should power the neck key closed.
The body octave pad should be open 2-3mm and no tension at lever to halo.
The finger from G to body octave roller sets the G key height.