Audio Issues with some programming via HBO NOW app

Long time lurker (thanks for all of the random help over the years), first time poster here.

I've had a Sonos system for quite some time, and have both a 3.1 setup using the Playbar, and a 5.0 setup using the Beam. My Playbar and sub are connected to my 'main' living room television, a Sony XBR900E (65 inch) via optical. The Beam and 2 satellite Play 1s are connected to a TCL 6 Series in my basement via HDMI. I've also got various other Sonos speakers throughout my house, so I'm familiar and comfortable with the system. A few other setup related notes:

- Verizon FiOS, gigabit service, no cable or satellite for TV (all apps/internet)
- Sony TV is set to output Dolby Digital
- Sony TV also has an Xbox One, Fire TV, Apple TV 4K, and Nintendo Switch hooked up to it, all via HDMI
- Apple TV 4K is also set to output Dolby Digital at all times
- No special settings for the Beam/TCL TV, aside from turning on CEC controls

My issue is as follows:

- When using the Sony TV/Playbar combo, I have ZERO issues with content from Netflix, Plex, Amazon Prime, Youtube, or over the air HD channels
- I recently re-instated my HBO NOW subscription to watch the latest season of Game of Thrones when it starts, and as a result, we now have access to Sesame Street episodes for my new son (wife was happy about this).
- HBO NOW content generally seems to work without issue, including multiple movies, old GoT episodes, and several other series that I tried watching
- No matter which device I use (native app on TV, Apple TV app, etc), I am unable to get any audio from Sesame Street episodes on HBO NOW through the Playbar. I tried both 'classic' and recent episodes.
- The 'about my system' info shows 'Audio In: Silence' when watching Sesame Street, however for any other content streamed from the HBO NOW app(s), I'm getting Dolby Digital 5.1
- If I stream the same content to my Roku-based TCL TV with the Beam, there are no audio issues. The Audio In shows as 'Dolby Digital 2.0' for the Beam in the 'about my system' screen.

I did try calling Sonos support, but all they were able to say was 'my best guess is that they are using either a codec or bit stream that is not supported'. While I understand that the connection is different between the Beam (HDMI) and the Playbar (optical), I would assume that they have the same limitations regarding codecs, etc, as they are running the same version of the Sonos software...so why is my Beam able to play this audio when my Playbar cannot? Is this truly an issue of optical vs HDMI connection? Some additional setting on my TV? Are both my Sony TV AND my Apple TV 4k incapable of converting this audio to something my Playbar can use? Any ideas would be appreciated.

Thanks,
Paul