m17 R5, display flickering only in optimus mode if refresh rate set higher than 60hz

My Alienware M17 R5 AMD laptop shows flashing black dots on the bottom of the screen. This only appears when I use Optimus mode and set the refresh rate higher than 60hz. If I use Nvidia GPU-only mode or set the refresh rate to 60hz, they don't appear anymore. It only appears if I use refresh rate higher than 60hz on Optimus mode.