I'm getting stutterings in different games when DX12 is enabled. Battlefield V, Modern Warfare, Shadow of the Tomb Raider. When I'm using DX11 (if possible) i've got a perfect frame time. When G-Sync disabled and I'm in DX12 mode everything is also perfect.
I'm always playing in exclusive fullscreen mode. If the game doesn't give over 144FPS I'm not enabling v-sync in games and I'm never enabling it in drivers. Different drivers didn't fix this issue.
Take a look at this sample from Zombie Army Dead War 4: https://youtu.be/nPsngiDqfKA

If I disable g-sync I won't have any stuttering. I can't say that EVERY game has stuttering issues in DX12 with g-sync, but I see that a lot of them suffer from this.
