".. one frame drop/repeat every 1,06 hour..."

It is normal to any Windows video player. Because of video synchronization to your display current refresh rate.
23.976 fps must be synchronized to 59.989 Hz. Numbers may be differ.

One frame drop or repeat in 1 hour is awesome result of synchronization.

otic wrote:

Because Nvidia is not able to keep their audio/video clocks at stable 23,976 fps

Why do you think so? I can't confirm.

Well, after setting 23Hz in NV control panel, then look at Ctrl+J Madvr stats and you'll see ".. one frame drop/repeat every 1,06 hour..." (the same when setting 59,940) and I can really noticed that.... With intel igpu-8700k in my case, Madvr stats show "...frame drop every 7 hours..." or more.

Maybe I'll take a risk and buy new CPU and motherboard...

Because Nvidia is not able to keep their audio/video clocks at stable 23,976 fps

Why do you think so? I can't confirm.

About i7 11700k integrated GPU. I have not access to this CPU but it have usual Intel UHD Graphics with 32 units. It can work with SVP to interpolate new frames up to 4K, I think.
But it seem it have not power enough to upscale or downscale video with madVR at high resolutions.

Of course, one neet to check If I wrong.

Because Nvidia is not able to keep their audio/video clocks at stable 23,976 fps, I' m planning to move to intel side. On Intel's hardware, I get stable 23,976 fps (also with 59,940) without any frames drops.... So, is new  Intel iGPU with 11 gen. CPUs-like 11700k, could handle interpolation with 60 fps? They say it's equal to GTX 1030...?