Perhaps try moving the speaker nearer to the local router and see if that maybe resolves the issue.

Exactly same probablem here, only era 100 with the problem, move, roam, beam and symfonisk working well. 
Sonos technical Support does not find a Solution. 
I am totally sure is a firmaware issue of the era 100 related to airplay 1. Airplay from iPhone or iPad works ok (Airplay 2). 
Last firmware update around a month ago.

really disappointed. 

Maybe see these links & requirements for AirPlay 2 …

https://support.sonos.com/en-us/article/stream-airplay-audio-to-sonos

https://support.apple.com/en-gb/101611

Edit: Note in the first link shown above, it mentions… "You can also use AirPlay 1 to stream system audio from macOS to Sonos, but you may experience a delay, or audio interruptions”.

Airplay 1 has works perfectly good for years…today still is working in all my Sonos speakers except Era 100…

I’m sorry I can’t really add anything further, as I usually just AirPlay from an iPhone, or iPad, and that seems to be working okay. What App/source-device are you using?

iTunes running on a win 11 machine. 
Raspberry pi 5 running LMS (lyrion music server)

Airplay 2 from iPhone or iPad or macOS works ok. 
 

With airplay 1 the Sonos app shows the Era playing, but no sound is produced. 
 

thanks 

This is exactly my problem.  I have a massive library on my computer so I have always used iTunes to airplay.  Stopped working on Era 100’s, but my roams work just fine.  I even tried moving to the windows “apple music” app, but that didn’t work either.  Over an hour on the phone with support and they couldn’t find the issue.  I can also play from my phone through airplay.

We need Sonos fix the the problem. 
I am 99% sure is a firmware issue.