SMPTE Timecode Framerate affects FPS stability

[elgarf]

Hi

I saw strange thing: the biggest SMPTE Timecode Framerate (STF) gives me rendering FPS stability decrease.

For example, if I set STF to 25, I get (almost) stable 60 FPS. If I set STF to 29.97 / 30, I get 30-40 FPS.
The bad thing is: I don't know why it's happening I have no SMPTE sources at all.

Copm size 1024x768, core I7 6700HQ, gtx 970m, 24 gb ram (MSI GS60 6QE).

[xergon]

Maybe the FPS Counter is just broken?
I recognized on Win10 with AMD R280X that fps jumped up heaps when using "no vsync" option, still 70fps looked and behaved more like 30fps. There were some more occasions when the fps counter didn´t reflect the action on the screen..