This concerns a multi monitor setup with different refresh rates (e. g. 1 with 60hz and 1 with 144hz).

The text below is part of the linked article. If you have both nvidia and picom installed, check both sections.

NVIDIA (propietary)

• Open nvidia-settings
• Go to 'X Server Display Configuration'
• In the bottom right, Click on 'Advanced...' if it says 'Advanced...'
• Make sure anything regarding 'force composition pipeline' is checked off
• Make sure you selected the highest refresh rates possible. You can either select it through the settings, configure it with xrandr or with your DEs Display Settings, is applicable

picom

• Make sure to start picom with --no-vsync

Misc

If it still doesn't work, try settings these environment variables:

CLUTTER_DEFAULT_FPS=<your highest refresh rate>
__GL_SYNC_DISPLAY_DEVICE=<your highest refresh rate display>
__GL_SYNC_TO_VBLANK=0

Find the DISPLAY_DEVICE name with xrandr | grep connected

Add the text block above to /etc/environment (Tip: Use EDITOR=<your editor, if EDITOR is not set anywhere else> sudoedit instead of sudo nano or sudo vim)

-> sudoedit /etc/environment