I recently purchased a Dell s2721dgf it's a 1440p/165Hz monitor and started using my old 24inch 60Hz monitor as a second monitor, my problem is that when I put videos (youtube, twitch etc on any browser or VLC) on one monitor and start playing a game on the other or even just do a simple click on the one that doesn't playback videos after 10-20 minutes the audio starts to desync from the video, moving the window to the other monitor doesn't help I have to refresh the page or restart VLC in order to fix it. What I noticed when it's a very long video, Youtube changes the resolution automatically to 480p.
I have tried turning off Hardware acceleration and changing the refresh rate of my old monitor and new to see if that helps but nothing changed.
Main monitor is plugged in through DP and my old one is with HDMI.
Specs: i7 8700k, GTX 1070