Youtube HTML5 video flashes in inverted colors once per second

When turning on the HTML5 player at https://www.youtube.com/html5 and playing any video, sometimes it starts flashing up with inverted colors once per second.

I don't know what triggers it, but it happens around 8 of 10 times for me.

Downstream bugs:

QupZilla: https://github.com/QupZilla/qupzilla/issues/1551
qutebrowser: https://github.com/The-Compiler/qutebrowser/issues/351

See the attached video - it started flashing right away which isn't visible in the video (dropped frames?), but after some seconds you see it in the video as well.

I also attached a screenshot of one inverted frame.