Finally got this fixed. it sounds like the reason for this is that since the latest update your phone cannot decide whether to use hardware or software back light settings. I managed to make the problem go away by doing this:
Go to settings >> system >> About device.
Find "Build number" and click 6 times fast on it.
You will then get the message saying: "You are now a developer"
Come back to Home Screen, and then go back to Settings >> system >> Now you will see the "Developer Options"
Now go to Developer options >> Drawing Section or Rendering Section >> Find "Turn off hardware overlays" or "disable hardware overlays" >> This will force the phone to always use GPU for screen adjustments. no more flickering.