This has been happening for me too. Funnily enough, I’ve had the tv I’m using for 2 years and occasionally on Netflix the background sound would drop off completely (music/noise, talking was fine). Anyways, I got a new tv a few months ago so this tv is now in my bedroom with the nowtv stick so naturally I assumed it was the tv being a problem. Messed about for ages trying to fix the audio on it to no avail. However I just googled nowtv audio issues and boom - this and many other threads are all showing it’s Nowtv not the tv after all.
Some dated back 2 years ago so I’m guessing it’s something to do with the upload on to the service being buggy. Hopefully now they are aware of it, and the fact that they’ve previously had all the other seasons on here without issues, means it will be fixed soon.
Wouldnt be so bad but it seems a high % of the words/dialogue missed are bloody interesting bits!
Also the Wire Season 1 episode 7, 8.30pm 11/10/2018. Problems started about half way through. Bleeps and bloops when fast forwarding etc. still make noises but the soundtrack breaks up and then goes silent. Viewing on Roku 3.