Image on the laptop screen slowly fades to white. If you torque the display or move it up and down the image goes back to normal. As soon as you release the display, the image stars fading to white again.
LCD screen failure.
The image fades to white because you have a failing LCD screen. In order to fix this problem, you’ll have to replace the LCD screen with a new one.
You still should be able to use the laptop with video on the external monitor.