Have you tried both a Displayport 1.2 cable and HDMI 2.0 cable?
Have you set the refresh rate to 144Hz in the Nvidia Control Panel? You could try setting it to 120Hz.
Unless you use the iGPU, uninstall the intel graphics driver and reinstall the Nvidia driver, the latest version is 512.77.
Since it's happening with both the iGPU and the 3070ti, it could be the cable, monitor setting, windows setting and as lalantha mentioned HDR mode.
Do you have Hardware-accelerated GPU scheduling turned on?