If you're using MSI Afterburner (+Riva Tuner) you could set the refresh time to the lowest and have a look at the frame
time rather than the frame
rate.
That way you'll see your fps from a different perspective. The fps are the "average over a second". If your refresh time is below a second you'll see a different average of course.
The frame time is in theory the same average since it doesn't measure the time between EVERY frame, but you'll see differences and jumps more clearly and with more detail, since the fps will be shown in integers/whole numbers whereas the frametime is simply shown in milliseconds.
MSI Kombustor Lakes of Titan 64 ; 1024x768 8x MSAA ; nvidia driver standard vsync and Riva Tuner FPS limiter used.
1000ms refresh time no limit/vsync:
View attachment 229154
1000ms refresh time with vsync:
View attachment 229160
100ms no limit/vsync:
View attachment 229155
100ms and locked fps:
View attachment 229156
100ms and vsync without riva tuner locking:
View attachment 229157
100ms + vsync + 60 fps lock:
View attachment 229158
Sometimes applications get some constant shimmering line until some bigger movement happens when you lock 60fps with vsync. 61 fps is a compromise then:
100ms + vsync + 61 fps lock:
View attachment 229159
Maybe this gives you some insight about what might be your issue