Chosen Solution
A long time ago, I had a white Macbook malfunction such that the backlight would flicker on and off randomly and for random periods of time before eventually failing to work at all. I replaced the backlight “ribbon” connection to the logic board and it worked perfectly. My Mid-2014 Macbook Pro Retina experienced exactly the same symptoms and I was wondering if it is possible to replace the ribbon assembly on this model? From an initial inspection, it seems like the display is assembled in a much less forgiving way for repairs, as the there is no physical trim holding the screen in place and all the aspects of the screen assembly seem permanently coupled.
I think, that you should do SMC Restart first: Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual.Hold down the Shift+Control+Option+Power button at the same time for a few seconds.Release all keys at the same time, then boot the Mac as usual. If that does not work, you could replace the screen. ( I have not heard, that you can open up the screen anymore ) Link: MacBook Pro 15" Retina Display Mid 2014 Display Assembly Replacement
