I have a 3810X and use Youtube TV frequently. This didn't happen until last few days. After it's been on live for a while there is a major video lag behind the audio . 5 seconds at least. I thought it was a channel problem (TBS), but then I hit home and reloaded Youtube TV and it works fine every time.
update: I'm fairly sure what's causing this is these occasional short commercials that don't seem to be actual commercials from the stream. maybe they are roku injected. also, changing the channel seems to reset it as well, don't have to reload youtube tv.
I'm having the same issue on all my roku devices as well as my Samsung note 9 which leads me to believe it's a youtube TV issue. I reported the problem on the youtube TV app under account, send feedback. Hopefully they fix the issue soon.