0. Your monitor has a refresh rate of 144 Hz. You cannot see 240 frames per second on a monitor that only refreshes 144 times per second. Cap your framerate at 144.
1. The version of Windows you are running has a limitation which causes performance issues in hardware accelerated applications (such as games) if multiple monitors with different refresh rates are present. Your system's monitors have 2 different refresh rates, so you are affected by this limitation.
To fix this issue, we recommend updating to the Windows 10 May 2020 Update. Follow
these instructions if you're not sure how to update.
2. Run OBS as Admin
3. Display and Game Capture Sources interfere with each other. Never put them in the same scene.
