So I can confirm that I have the same glitching as the Example above and I did a bit of testing.
I opened the link up in 3 browsers on 2 systems.
First is my i7 Win7 PC and the other is my i5 Win7 laptop.
I used Google Chrome 50.0.2661.102, Mozilla Firefox 46.0.1 and lastly Internet Explorer 11.0.9600.18204 (I know I know, this was for science)
All 6 instances had the same glitch at the same point in the video.
It struck me as odd that I cannot recall any glitching during the (half)day off of Enter the Gungeon nor the first 3 parts of Sellaris which makers me wonder if the glitches only occur in hearthstone vidoes. If so, this could indicate a problem with the capture/recording of those streams?