Re: power button and camera
I've never seen this. Is there a chance that you are doing the twist to open camera gesture at some point when you are not actively using the phone (like, when it's in your pocket or a case) and the screen is turning the camera on and then powering off without you being aware? Or does this happen even if you turn on the display, press home to go home, turn the display off and then on again? I suppose to check for this, turn on the camera, drag right from the left edge to open the settings, swing the settings arc up to the lowest entry and turn off the shake to start camera gesture and see if that stops your problem.
The only other thing I could think of is settings / accessibility / double tap home is set to "Camera". There is a known bug in the KitKat build where a single key home press is mistaken for a double press, but that doesn't happen in this case - I just changed that setting to camera and it took a true double-tap to get it to open, so that's not the cause.
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