It's going to be either a failing connection or cable.
Did you replace the cable that goes from motherboard to the display?
I have an old Sony Vaio Model VPCEA laptop running Windows 7 64 bit which I would like to upgrade to Windows 10. However I have a screen problem that I would like to sort out first. Whenever I move the screen back and forward the screen sort of flickers. It doesn’t go black or anything it just sort of goes slightly darker and then brighter again. I used the Vaio Care function to test the display and it passed as okay. I went onto the Sony eSupport site and downloaded the latest Intel Graphics driver which was dated 2013 and installed it but that made no difference. Does anyone have any idea what the problem could be and is it something I could fix? It’s almost as if there is a loose connection or something but usually the ribbon cables on these things are very secure so I don’t want to mess around too much until I have a better idea what the problem may be. Any help greatly appreciated.