Hi @Søren Langelund 

Welcome to the Sonos Community! And, apologies for the delay.

Sorry to hear of the issue you are having in listening to your stereo pair of Era 100s, though I’m not entirely sure what problem you are having. Speaker performance issues are usually due to local conditions, so I recommend a read of our reducing wireless interference help page, and removing any possible sources of interference near your speakers and/or router.

It may also help to reboot the speakers and/or router - if rebooting the router, please switch it off for at least 30 seconds.

If none of this works, I recommend you get in touch with our technical support team who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports.

I hope this helps.

I have see a similar issue using a pair of Era 100s as surround. One is losing its connection to the group and either shows as a separate speaker or as offline. 

Similar problem. 2 x Era 300 as separate speakers or a stereo pair. One speaker disconnects from time to time. Always the second speaker added to the system in the application.

The problem occurs in the Sonos app on iPad, Android, Windows. Also in the old Windows and old Ipad app.

The problem occurs when I play Apple Music. Also when I use AM via Airplay too. The Sonos app shows that both speakers are playing and then stops responding to pressing the control buttons.

The problem does not occur in Spotify.

Technical support suggested connecting the speakers to WiFi via the phone's hotspot, but it was not possible to connect the speakers to the system or create a new system on this network.

Replaced Technikolor modem-router from the Internet provider. Router configuration by a network specialist. 5G network.

Restarting the router, app, AM and speakers helps for some time, but the problem returns.

Maybe there is an easy way to fix the system without hours of discussions with Sonos support?