I had an end user have the exact same video problem that you are having. She found that if she flexed the top-left of the display housing, the problem would go away. Eventually it got worse and she had to hold that flex position to be able to use the laptop. I thought it had to be a bad connection. Possible the flex cable or just reseating the cable into the connector at the bottom of the display. I opened up the display assembly and with it powered up determined that it was not the flex cable but somewhere on the circuit board that is attached to the display panel. Pretty small components on there. Replacing the LCD panel solved the problem.