November 2019
This happens frequently for me as well. The audio doesn't just die though, it gets distorted and weird, but perhaps it's just because certain voice channels are dead.
It made me suspect that there is a memory bug somewhere though, that is corrupting the sound files in memory.
I don't even know if that is possible with today's OS's and apps, since memory handling should be pretty solid.
I'm using a Pixel 3 XL.
January 2020
I'm still having this issue. It's been months with no fix.
GooglePixel 3 XL in USA.