Do you have access to their TV? I'm going to guess that the TV output to their soundbar (which one?) is set to variable, so it's reacting to whatever the setting is on the TV set at the time. If you can go into the audio settings for the TV, and switch the optical output (I'm making an assumption here) to "fixed" rather than "variable", that might be the issue.
It might be useful to let us know what the make and model of the TV is, what the source of the programming is (Cable? DirecTV? Over the Air?) and what the soundbar is (PLAYBAR? PLAYBASE? Beam?) so that we can be a bit more specific, if the above doesn't fix the problem. But that's the only explanation I can come up with that would affect both the PLAY:3s and whichever Sonos soundbar they have.
I'm not sure that there are "many" who are experiencing this.
OK, gotcha. Not that familiar with the LG series of TVs, but I do know a bit about the Sonos system, so I may be able to help you, or you may need to ignore me, and contact Sonos on one of their true support lines, rather than the community here, but let's see.
It's unfortunate that the TV doesn't have a setting to change the output signal, but I guess that would have been too easy of an answer.
I had to go back and reread your original post, as we're not actually talking about surrounds here. Saves some discussion about 5Ghz etc, but that's not important here. Since they're using a BOOST, then the Sonos devices should all be on the SonosNet network. When you look in the controller, under ...More and About My Sonos System, all of the speakers should be showing up as WM:0. If they're not, you may want to go into the settings for the wifi, and remove any data that's there. I think there's an "erase" or "delete" button. What you're trying to do is make sure there's only one way for the speakers to connect. The software is designed to take the lowest cost path, but depending on the situation, it might be their wifi, it might be the Sonos wifi, and the waffling between the two would certainly cause dropouts. So we remove the wifi data, and rely on the SonosNet data, the way they were originally designed. And in that case, they might be going back to the BOOST with the signal, but it's much more likely that they're going straight to the PLAY:3s on the mesh network.
However, all wifi signals are subject to
wifi interference. That's either from inside the LAN, or even outside. It could be that there's a neighbor's signal, or microwave, or phone, etc, that's causing an issue, so it's worth reading that FAQ and checking all the boxes.
But wifi interference could only explain volume issues on those grouped rooms with the PLAY:3s in them, it wouldn't explain the change in volume on the PLAYBAR, since that comes directly from the TV set across the optical connection, and there's no interaction with a wifi signal at all.
Have you been there when they've experienced one of these volume reductions? I'm really wondering if it's only with the PLAY:3s rather than on the PLAYBAR itself.
One of the things to double check on that TV, though, which might explain "some" cutouts, is that the audio settings are locked down to Dolby Digital. I've seen on some channel, a few years ago, when they put one of those scrolling text bars across the bottom, they accidentally pushed the sound to DTS (or something that my PLAYBAR couldn't interpret), and when the scrollbar went away, I got sound back. Took a while to figure that one out, fortunately it was on a DVR recording, so I could replay it several times. But once I locked down my source (DirecTV and AppleTV) to be only in Dolby Digital, rather than "Best Available", that issue went away.
It strikes me when I reread the description of the setup is that the PLAYBAR might be being controlled by a remote control. I don't remember if you can remove that, but it's worth looking at the potential that they're unknowingly changing the volume of the PLAYBAR with the remote control (sitting on it? who knows!) However, changing the volume of the PLAYBAR would not affect the grouped rooms, which may be why there's a perception difference there.
It's hard to diagnose and suggest solutions remotely for something like this, I suspect you're feeling much the same, since you can't always be there when it happens. But if there's any way that you can convince these people to
submit a system diagnostic within 10 minutes of having this problem, and writing down the number, you could then
contact Sonos to discuss it. There would likely be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
Oh, and if you're still with me after this giant wall of text, there's one other thing I'd recommend, which is low cost, low effort, and might potentially help. Unplug the Sonos devices from power, and then reboot the router. Once the router comes back up, after a minute or so, go ahead and plug back in the Sonos equipment. What that will do is force the router to reset its DHCP table, and the Sonos devices will get new IP addresses as a result. There's a slight possibility that the router handed out duplicate IP addresses the last time the system was updated.
Let us know how you get on. And even if you can't call Sonos when you're at the location, you might be able to talk to their 24/7 support folks via Twitter or Facebook. I'm a fan of the phone conversations, myself, it gives them the opportunity to do some remote looking at the system, but that may not work with the timing of your visits.
Good luck!
