Just a guess, but perhaps Netflix on the Shield is sending dolby digital plus rather than dolby digital?  Might be good check the audio settings for the Shield and Netfilx.   

To clarify, is it always stereo on Netflix through Shileld, never 5.1?  Or is that the case sometimes?

Thanks for the quick response!

It does play in 5.1 on the SHIELD, but only sometimes. If I were to play movie X on the TV itself it would play in 5.1 but when playing that same movie on the SHIELD, it would play in stereo.

I have checked the input information multiple times, and it says Dolby Digital Plus. Is that a bad thing?

I have also tried selecting different audio types manually, which made no difference.

A good example is also the Netflix start sound; it plays on all speakers on the TV, but only on the Beam when starting Netflix on the SHIELD.

The Beam cannot play Dolby Digital Plus content, so yes, this is a problem.  I’m not sure if this is an issue with your Shield settings, or a problem with the TV not telling the shield what audio content it can take.  

Since you know DD+ is a problem now, perhaps you can revisit the settings one more time to make sure everything is correct?  If that doesn’t work, no one else here has some suggestions, than you could try using an optical connection between the TV and Sony.  

I just tried using an optical connection, and it seems to be working fine now!

I still think it’s weird the way HDMI doesn’t seem to work properly since it works using the TV itself. I also tried manually setting the audio signal to Dolby Digital on the SHIELD which didn’t make a difference!

I never even thought about an optical connection as a resolution and can’t believe I managed to solve this problem within an hour! 
I’d still live to know why HDMI worked on the TV only.
 

Thanks a lot for your help!

Edit: Just checked the Sonos app while playing Netflix and it says Stereo 2.0. Is this normal?

Edit 2: Just found a setting on my TV to change the SHIELD sound to Dolby Digital instead of Dolby Digital Plus and enabled it. Sonos now says Dolby Digital 5.1, but there’s no sound from the rear speakers. This is with both HDMI and optical connections.

Update: I just figured it out. I’m a Brit living in Germany and use the German Netflix to watch English content. Turns out, some content is only available in English without 5.1 but the German version is available in surround. So I guess Netflix is to blame and definitely not Sonos.

Weird thing is, when content that isn’t available in 5.1 plays on the TV itself, it only plays in stereo 2.0 of course but does play sound on the rear speakers.

The SHIELD meanwhile doesn’t do this, non-surround content doesn’t play through the rear speakers, which is annoying.

What setting on your TV did you change to get the shield to output 5.1 to your beam

There was no setting on the TV I needed to change. The content I was playing simply didn’t support 5.1. Due to the fact that the German Netflix doesn’t offer 5.1 on some content in English but does in German, I’m now using a VPN to access the US Netflix.