Lines on the screen - LG 24MK430H

@kyramai Those look like Tab errors but can also be caused by bad LVDS f;lat ribbon cables. First make sure that those cables are properly inserted. Check for any torn edges or corrosion on the ends. you can clean them with some isopropyl alcohol and a pencil eraser..If all of those check out okay, then this would be a Tab error. That is where the "bonding" that adheres the thin ribbon cables to the actual panel, comes loose or corroded. Take a really close look at those and apply some gentle pressure on them. You will most likely see that the lines either change or disappear That is incredible difficult to fix but sometimes some downward pressure applied y some adhesive tape etc. can make them go away for a while at least. If you have trouble identifying the ribbon and Tab just post some more images of what you see on the top of your LCD panel. It should look something like the images I attached.

For illustration purpose only