I have had this problem too. My "home" button would only be in the correct place of the screen in the scene where my character starts from the spot the camera automatically starts in (I've understood that the camera always first goes to the top left corner? (I found this out because my character was spawning in the wrong place because of this)) So I solved this problem like this:
When i place the button to the scene I make sure I have scrolled to the top left. I put on the Screen Bound grid and place it in the highlighted square where I want it.
So basically the Screen Bound button shows how big the camera screen is when you play, and it starts in the top left corner even if you character is somewhere else. So place the buttons there inside of the highlighted area! This worked for me.
I hope this makes any sense.. :') anyone pleace correct me if I'm wrong..