Windows has a long-standing bug when running multiple monitors at different refresh rates. It was supposedly fixed in the Win10 2004 update (you are on update 2009), but still presents on some systems. It appears you are running 60hz on one monitor, and 120hz on a second monitor.
There are multiple ways to test for this.
-Move OBS to the monitor with your 3D accelerated application/game while recording.
-Right-click the OBS Preview window and Disable Preview.
-Set all attached monitors to run at the same refresh rate.
If doing any of those three fix the problem, you are affected by this Windows bug.
As a side-note, Monitor Capture is the WORST capture method available, and should be avoided if at all possible in favor of a Game Capture and/or discrete Window Captures for each window you want to show on-stream/recording.