The only fixable cause of that symptom is a display cable problem. The flex cable is not infrequently to blame. If squeezing somewhere on the edge of the lid around the display makes the bars go away intermittently, then that pretty much cinches the diagnosis. The solution is to disassemble the lid, remove and reinsert the flex cable where it connects to the display panel, and repeat as necessary. This action cleans off the small amount of oxidation that has caused the problem.

That said, a cable problem typically wipes out larger regions, not just single lines. But try the squeezing exercise anyway.

Good luck!