I don't think it's to do with OBS, it's a hardware glitch from either driver or firmware reacting to something Windows 10 brought in at the beginning of November. It's been driving me mad for the past month, I'll be playing a game and then just randomly the FPS will drop to 1 or 2 and I have to exit the game, I open Task Manager and both Client Server Runtime Process and Desktop Windows Manager will be using 100% of the GPU between them leaving every app or even mouse movement a laggy mess. I still can't track down what causes it, just that it has only happened since the Windows 10 Fall Creators update, and it can happen after 10 hours or 10 mins.
The only thing I'm sure of is that it seems to be on the hardware side because the best workaround I've found so far is to hibernate the computer and then wake it up again and the glitch is gone, proving that whatever is causing it is not in memory and instead must be triggered. I'd wager that it is to do with throttling or power saving or the like.