Graphical problem with Radeon graphic card

I do not know where to exactly post the issue about technical issues, so I thought this is the best place.

I have built a new pc with a new MSI 5700xt Mech OC for my little brother. The screen very quickly and briefly flashes a dark line across the screen and occasionally flashes some white screen very quickly (has a 144hz monitor). Sometimes a match in normal made the entire screen stutter and freezes every second or so. I have checked that all drivers are up to date (used DDU just to be sure), switched the monitor cables and the whole monitor itself, and the problem still appear only in League while other games are fine. We even ran a benchmark on 3DMark Time Spy and it scored with no problem. I even let him switched my 2070 Super with his graphics card and the problem went away, indicating the problem lies within the Radeon graphics card - and only on League for some reason.

Can anyone help me identify the problem here? I also noticed that League of Legend application does not appear in my AMD Radeon settings. Can someone direct to the location of that application so that I can add the application in and optimize it with AMD Radeon Settings? Thanks