Laptop Screen acting weird

My sister's laptop's screen has been acting weird lately. She opens the laptop screen at a specific angle and all is fine, but when she tilts the screen to close it or change the angle, the screen has bars like it has a loose connection or something (I don't really know how to explain it). Is it a hardware problem (maybe the cable isn't attached completely?) or is it something that is wrong with the screen itself.

She has an HP laptop by the way.