That's most likely some specific app setting, and no one can help you besides yourself in this case.
Look for any app running in the background that could record videos, such as any video recording application, the GeForce experience (Nvidia Shadowplay) or the AMD Gaming Evolved (GVR/Plays.tv) apps, not to mention MSI Afterburner's bosom buddy, the RivaTuner statistics server.
In any of those apps, find out the hotkey settings and remove the (un)desired keystroke combination.