Once the octave pin is properly positioned, the last potential issue is a bent arm at the base of the neck. This can cause the pin to sit up against the arm too much and lift the pad off of the neck even when the key is not pressed, or potentially not lift the pad enough when the key is pressed.

Gently pull the base of the arm towards you and away from the neck if the pin is pulling on it naturally. Gently press and bend it towards the neck if the pin does not properly pull on it and lift the pad when the octave key is pressed.

Once again, this part is very delicate. Too much bending can cause it to break. Use small adjustments when fixing your octave arm.