Can you provide more information? Does this always happen? We're not seeing this in the a/v lab so seems specific to your system. Can you provide more details on your setup?

It happens most times, but not always, and even happens sometimes if the video has been paused for a while.

I am using a plain z840 with a headphone jack, using basic earbuds. I don't think there's another special about my config as I've not customized anything. 
This is an official build I'm running. 

Copied from chrome://media-internals under the audio stream tab

[
  null,
  {
    "171:1": {
      "channel_layout": "STEREO",
      "channels": 2,
      "component_id": 1,
      "component_type": 1,
      "device_id": "default",
      "device_type": "pcm_low_latency",
      "effects": "NO_EFFECTS",
      "frames_per_buffer": 512,
      "owner_id": 171,
      "render_process_id": 177,
      "sample_rate": 44100,
      "status": "stopped",
      "web_contents_title": "✨ KIR Media UX ✨ - Chat"
    },
    "439:2": {
      "channel_layout": "STEREO",
      "channels": 2,
      "component_id": 2,
      "component_type": 1,
      "device_id": "default",
      "device_type": "pcm_low_latency",
      "effects": "128",
      "frames_per_buffer": 1024,
      "owner_id": 439,
      "render_process_id": 104,
      "sample_rate": 44100,
      "status": "stopped",
      "web_contents_title": "https://beaufortfrancois.github.io/sandbox/media/mse-blob-download-alt.html"
    },
    "780:8": {
      "channel_layout": "STEREO",
      "channels": 2,
      "component_id": 8,
      "component_type": 1,
      "device_id": "default",
      "device_type": "pcm_low_latency",
      "effects": "128",
      "frames_per_buffer": 1024,
      "owner_id": 780,
      "render_process_id": 79,
      "sample_rate": 44100,
      "status": "stopped",
      "web_contents_title": "Facebook"
    },
    "784:9": {
      "channel_layout": "STEREO",
      "channels": 2,
      "component_id": 9,
      "component_type": 1,
      "device_id": "default",
      "device_type": "pcm_low_latency",
      "effects": "NO_EFFECTS",
      "frames_per_buffer": 512,
      "owner_id": 784,
      "render_process_id": 79,
      "sample_rate": 44100,
      "status": "stopped",
      "web_contents_title": "Facebook"
    },
    "785:10": {
      "channel_layout": "STEREO",
      "channels": 2,
      "component_id": 10,
      "component_type": 1,
      "device_id": "default",
      "device_type": "pcm_low_latency",
      "effects": "NO_EFFECTS",
      "frames_per_buffer": 512,
      "owner_id": 785,
      "render_process_id": 79,
      "sample_rate": 44100,
      "status": "stopped",
      "web_contents_title": "Facebook"
    }
  }
]

edit, that was everything under the audio tab. 

Doesnt seem to happen when youtube automatically advances to the next video. Seems to only happen when I initiate playback by clicking a link or by pressing play. 

There's nothing unusual in the media-internals. Sometimes you might see something like this happen with HDMI connections through a receiver, but I'm never seen this on a Linux machine through the minijack. Does this persist across reboots? Or a pulseaudio restart?

I've rebooted my system and it seem like occurrence have lowered (currently zero, but I thought I might have heard it happen on an ad). I'm going to monitor next week to see if I find it happening again. If it doesn't occur, I'll close this bug out?  

sgtm, => for tracking

Yeah its still happening. 

Does this happen in an incognito window with extensions disabled?

So this still seems to happen in incognito, but perhaps with less frequency. 

Forgot about this, are you still seeing this?

Yep, although the frequency has dropped. 

What value do you have for chrome://histograms/Media.LinuxAudioIO ?

Histogram: Media.LinuxAudioIO recorded 1 samples, mean = 0.0 (flags = 0x41)
0  ------------------------------------------------------------------------O (1 = 100.0%)
1  ... 

That's pulse audio then.

How about with --disable-features=AudioServiceAudioStreams,AudioServiceOutOfProcess ?

lethalantidote@, does this still happen? Can you try with the flags mentioned in #19?