About Gsync/Freesync from what I've read :
If you go above your display's maximum refresh rate, there will be no more forced sync with the display, as if you go under the minimum which is 30FPS for Gsync and 40FPS for Freesync (if I'm not wrong about those numbers), the sync will stop until you go above the minimum Gsync/Freesync range.
So if you play a game where you are above 144FPS (which seems to be the case from your screenshots on your original post), Freesync will wait you go below 144FPS to do its job with your display. Then you go above 144FPS again, it stops, works again, stops, this may cause stutters.
All you can do is cap your max FPS in the drivers to 141FPS to be sure you never go above the maximum refresh rate of your display when you have Freesync enabled to prevent Freesync to stop doing its job.
For Gsync, people say you better disable Vsync while using it, to avoid frame drops. It may be the same with Freesync.
Now if you experience stutters only in 1 game with Freesync OFF, it can be the game x)