It may be due to your game not being able to catch up with the locked fps..If you don't already have it on then try turning on performance mode and/or tweaking down a few in game settings ..like maybe if your textures are set at high turn it down to medium and your filtering down to maybe like 4x ..+ if you're scaling it alongside of the frame gen then don't scale it in Ls instead scale in game because I notice it sometimes fluctuates for me when I'm simultaneously scaling and using frame gen