I've been experiencing this problem off and on for a while now, I'm unsure of what triggers it.
I'm currently using a 2022 G14, 6700S with the dGPU mode enabled.
The captured FPS is always about 10-15 FPS lower than the ingame FPS captured by Riva Tuner.
I remember seeing a comment on reddit that addressed this issue as a problem with Windows, something Microsoft needs to fix. But considering that it isn't always a problem for me, maybe there's something to address here.