Sounds like the lcd controller is giving problems. Could be physical damage (blow to top of screen) or age. IMnsHO this is not a DIY repair, you could however replace the LCD screen (comes with a new controller board) rather easily. Once you get the back of the case off the display you can read the LCD part number... you can see the amount of work needed to swap the controller (it's a lot and it's delicate) you know your limitations.
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