Just started having problems with the display backlight not turning on when I push the power button. The phone is waking up. If there is a very bright light in the room I can see that the screen is working but there is no backlight. Sometimes it works fine. Sometimes it lights up as I push the button then goes black as I let go of the button, then I can hear it relock after a few seconds. I tried taking it apart and cleaning the power button with some compressed air which seemed to help for a few days, but then got worse.