Random graphical glitches while watching a movie

Hi all,

I have this old HP ProDesk PC which i'm trying to turn into a mediacenter.
It has an i5-4570 and an old RX 560 (2 GB variant)

Every 5-10 minutes or so, the screen goes green, and then blue. I can see the UI and movie fine through this blue but it's very annoying, i have to replug the HDMI cord to fix it. Anyone that can help me?

Forgot to add: I don't think my GPU is dying, it worked fine in both Windows & Linux.