It sounds like you've made some progress by prioritizing your Sonos device on your Linksys router. Network prioritization can definitely help with performance. However, if you're still experiencing issues, it might be worth checking if there are any firmware updates for your Sonos devices or router. Sometimes, improvements in the software or firmware can resolve lingering issues. Also, consider reaching out to Sonos support for further troubleshooting if the problem persists.

What I would also suggest is, since your beam is only 3 feet from the router, connect it to the router with a cable to see if things improve further.

Check the Beams settings to ensure WIFI remains turned on.

This is just for troubleshooting, but if it solves your issue, consider making it permanent.

Ok, I ran the ethernet cable to the beam, and it did play non-stop without skipping for about an hour, until it suddenly stopped playing, and the app (Android) said “No devices connected”. I didn’t touch anything.

I guess that’s progress, but I can’t understand why it stopped, unless something goes to sleep.

Try removing power from everything: router/network, and all Sonos devices. Wait 5 minutes. Clear cache on mobile app while waiting.

Then starting with the router, power it up and wait for it to fully boot. Then power on the Beam, then the other speakers. Leave the Beam hardwired and test again.

It still skips songs and stops playing altogether,  even connecting through a direct ethernet cable!

We started experiencing a similar issue today while playing a Sonos playlist containing songs from our music library (SMB share). It would play between one to five songs and then randomly stop and jump back to the beginning of the queue. We're using the Windows app to select playlists and manage queues, because the Android app doesn't recognise our music library and existing playlists. 

We haven’t changed anything in our Sonos hardware or home network setup for years, and all was working well before the recent firmware and app upgrades. Since then we have experienced a multitude of issues with the Android app, as reported ad nauseam here and elsewhere, but have still been able to play music from our music library using the Windows app. However, since today even that is no fun anymore.

If you submit diagnostics and call Sonos Support they will be more likely to put the problems on the fix soon list.

MANY are having same or similar issues. SO many of us have spent thousands on this proprietary equipment for it to only not work properly most of the time. If SONOS is not going to fix the issue, I would think enough of us should get together and class action !