Tuning in to report that I have the same problem. Two devices connected via ethernet (LAN) that can find each other without problem (can ping each other) where audio stops and resumes every minute or so. Tried all the different things, both machines are up to date, the software is up to date.
I tried a suggestion posted by another user, to restart the audio service using "restart-service -Name Audiosrv" in elevated powershell which fixes the issue right away, just like changing certain settings in the multiplicity audio settings does. It's really a bummer that this audio feature isn't working reliably because the entire application is extremely useful and convenient.
I don't know if this was changed in an update in the meantime, but no Multiplicity Audio Device appears in my list of Audio Devices.
I can also report that my secondary PC (the one sending audio) has some built-in audio switcher that changes the output device based on what ports have a device connected. I don't connect or disconnect any devices when the audio is cutting off (or ever, really), but just thought that might be useful to know.
My suspicion is that this is indeed something Windows related. Sometimes it works just fine and goes for hours. It's been working fine for the entire duration that I've been writing this reply. Hoping that a solution can be found 