Most of your missing frames are due to rendering lag. Run OBS as administrator, as this will put OBS on the GPU priority list to give a better chance of giving it the necessary resources to keep up with frame grab timing.
Run a test as admin, and post another log file.
There's plenty of other things that may be affecting things as well:
- Monitors at different refresh rates
- CPU may be overloaded running at medium preset (ensure OBS priority set to High, try lowering preset)
As a side note, once you work out the rendering lag you may want to try Nvenc encoding. The quality is basically on par with the medium preset, and it will mean your CPU doesn't have to deal with the extra load of encoding. Just make sure not to use the Max Quality preset, and leave Psychovisual Tuning and Lookahead off.