I contacted YouTube TV support and the first response was the usual "Uninstall the app, power off Roku, power off Internet modem (lol), reinstall app" but it's the same. After a restart of the Roku it's fine, but if I use Netflix and then go back to YouTube TV, it's the same again. They asked for video samples which I sent today, so I'll see if I get anywhere with them.
I'm also starting to see it happen with more channels now. I tried to watch sports on Fox and Fox Sports channels and saw it there, as well as PBS and ABC. Others are fine though like CBS, TNT, NBC.