Disable any other game overlays or overlays like steam etc. this looks like overlay flash. Since there's no log I can't say for sure if you are using AMD or NVIDIA, if using AMD try disabling Freesync or Relive, relive first. Anything that can popup in game over your game in fullscreen is an overlay so if you know what you have running that does this, shut it down and check to see if it still is happening, in game capture you can also try checking and unchecking the Capture in-Game Overlays button...
If you have afterburner running or RIVA try turning those off for sure as that can usually be a source of frustration with or without capture active.