Hi,
Try connecting an external monitor to the laptop and check if its display is OK.
If it is then you may have a hardware problem.
It could be a loose video cable connection to the systemboard, a faulty video cable (trying pressing on the left hinge area to see if you can make the problem come and go) or a faulty LCD panel.
Here’s a link to the service manual for the laptop.
Scroll to p.85 to view the necessary pre-requisite steps and then the procedure to remove the display assembly.
This should give you access to view the cable connection first.
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