Hey @JesusOfCarrots could you take a glance at my answer and let me know if your issue relates to what I described?
You marked your post as Solved, is it solved by the hack of changing the theme or something else?
Edit: re-read your post and saw you’re on windows and experiencing flickers mostly when using Youtube. As our issues might difer, I created another thread here: Whole window Flickering in full-screen mode with popups