The Boost isn’t needed here, will not help; when you say that the pair is wired, what does that mean - are both independently wired to the router/base station?
Thanks, Kumar. When I say it’s wired, I mean that one of the speakers are wired to my network so all of the speakers are on Sonosnet as opposed to my WiFi network.
There’s something fishy going on because the speaker doesn’t drop out if it’s not paired to another or if I’m not grouping it with another one (i.e., as a single speaker, I never lose audio). It’s only when I pair it or group it with the other speaker that I eventually lose audio (music starts but skips through tracks with the “not encoded correctly” error, total drop out, etc.). Yet my speakers are not that far apart and WiFi is pretty strong everywhere in the house. I’m starting to wonder whether it’s a bug with the latest system update.
Assuming that all speakers are in line of sight of each other, try wiring just the left( master) speaker of the stereo pair and none of the others and see if this improves matters.
But after the wiring change - or not if that is already how things are - power off everything including the router and then repower/reboot in this order: modem, router, wired Sonos units, wireless Sonos units.
Does that help?
Also, when using any speaker, or speaker pair in grouped mode, start the group with a wired speaker and then see if the issue still surfaces. In grouped play the first speaker selected is the coordinator and it helps stable play if that one has a good connection as a wired speaker would have.
I can’t wire either of the paired speakers, only one of the other 3 Sonos devices in the house (2 x One SL and an Amp, to go along with the two One SL that are normally paired in the kitchen). I’ve gone through so many complete shutdowns of my network to try and get this working that I’ve lost track. The dropouts don’t happen right away either. They only tend to happen after about 20-30 minutes of problem-free playback. Then when it happens, I have to wait a while for the affected speaker to come back online. It’s like it needs to cool down or something. 
I have strong wifi throughout the house although I rarely use 2.4G. Nevertheless I’ve changed the channels (1, 6, 11) there many times but it’s never helped, whether using Sonosnet or my own WiFi network.
I even physically swapped the speakers because I suspected a hardware issue but the problem does not follow the physical unit.
For these reasons, I’ve just about written it off as a bug that I hope Sonos can figure out. I’ll probably replace them with a couple of HomePod minis to see if I have better luck.
Submit a diagnostic the next time this issue crops up, and send an email to Sonos Support, mentioning the diagnostic number you are returned. You can also quote that number here for Sonos staff on this site to pick up and respond to.
@DerekF Go to Settings/System/About My System. Do all the units show “WM:0”?
If not your system is in ‘mixed mode’ which can cause this kind of problem. Post back.
