Well, I've made a bit of progress...I believe I have the third in play and I've discovered some of the....ah...electromechanical properties of the sphere...
But I just wanna say, I recommend WD-40 for everyone. A little spray into the button and the thing's a fluid wonder. Yay WD-40!
Your Isis is factory prepared with the correct amount of lubrication within it. If the rings and button on your Isis are a little stiff to operate apply 1 drop of light machine oil such as 3 in 1 to each ring and the button. Don't use penetrating fluids such as WD 40 as they may have a detrimental effect to the operation of your Isis.
Well, after pressing the plunger several thousand times, I can assure you that it no longer had the proper lubrication. I was careful to use a very minimal amount of WD-40, and it's been fine ever since. I've reached the halfway stage, in any case! = D