Hello there
Here is my technique for fixing unresponsive buttons.
Since spraying button with deoxit f5 or prf 7-78, means you need to spray a loooot for chemical to reach oxydized connector and probably flip hole thing up side down due to the button design, and probably most of chemical ends up on the motherboard 
So developed adequate method for this situation,
you won’t even need to take your machine apart, just remove button cap.
Here is what i used
I used 0.45 mm needle for suringe and slightly bigger sawing needle to make the holes.
I’ve heated the sawing needle to make small hole from the top of the button, and then inject contact cleaner of your choice thru the hole with suringe.
Because you are injecting chemical from the top, it will affect spring and ball from top all the way down to contacts on the bottom.
Also,while inserting needle you can feel the ball and you can gently try to move ball around to change its position, meaning also probably moving away oxydied part of the ball.
Of course it require to click button few times to get everything working but eventualy it starts to live again.
Drop of some glue should close it if you dont want dust to go inside thru the hole.