ORIGINAL: Ragz
Craig, my install is an identical copy of yours.. and it leaks more often than not. I have set it up in such a manner that the button is completely pressed when the gear is up...but every now and then I find that the gear has not reached the exact same place to compress the button.
Ragz
In that case, I would try the mechanical arm like Harley suggested. I would also make sure you are positioning the button with the jet upright, such that whatever "droop" there is in the gear is accounted for (i.e. with negative G it just pushes against the button, rather than away from it with positive G), if that makes sense.
I also still believe you have a bad button. I would get a new one regardless because it should not leak air under any circumstance.
Craig