Also, here’s a screenshot (from the video)
Also, here’s a screenshot (from the video) with the artifacts visible. I notice they seem to cover mostly just Chromium’s content area, but just last night I had this occur just as I was logging out (with the lines remaining on screen until I tried to take a screenshot), with nothing but the log out confirmation running on top of my desktop, so it’s probably not just Chromium that’s causing this.