Auto detect dolby 5.1 setting causing audio pops in X1 Youtube app on Vizio TV speakers

I have a question about Xfinitys Xg1v4 box & sound.
I use an xg1v4 plugged into a Vizio tv. I use the built in TV speakers. The sound settings on the x1 box has always been on Auto Detect Dolby 5.1.
For a couple years now, ONLY WHEN watching YouTube via the Youtube app on the X1, i would get this random popping noise from my left speaker.
I swapped out the tv speakers. It didnt fix it.
I was thinking maybe it was the main board and was going to swap the main board.
Its been swapped before but that was bc of a blank screen.

So just now i turned the sound settings from auto detect 5.1 to STEREO and havent heard the popping.

Could that auto detect Dolby 5.1 setting have been causing an intermittent popping sound like that? Always from the left speaker? Because im not using a 5.1 setup?

why only on x1 youtube app specifically?

Should I be using Expert Mode or Stereo for just the built in Tv speakers?