Had the "same" problem. I replaced the power button, now it clicked but still no action. Then i saw the bezel frame was not sealed 100%, i just pushed on it a little and then power worked. So everytime need to use power button i have to hold the screen and frame pressed together so the button gets a connection. This might not be the solution for you, but this was my experience. :)
Same exact problem that I have. I think it has something to do with the glass touching the ipad. Something like on the iPad mini, where you had to cover some areas beside the home button.
I would love to see a real solution, as im stuck with unhappy customers and frustrated me :)