Hello @CRo,
Thanks for contacting with us regarding this issue.
We have seen this issue before with Linux based Core and Android remotes and the solution for a majority of users was to disable IGMP snooping as Fernando has mentioned, but since you do not have this option it will be a much trickier to narrow down where exactly multicast is going wrong in your setup.
There has been quite a lengthy discussion regarding this issue which you can read about in the thread Fernando linked above, a few Roon team members also chimed in including in this post by Mike and we have repeatedly tried to reproduce this issue on our end without success.
Although it is not ideal, we have found that this connectivity issue mainly affects Linux based Cores and Android based Remotes, so if you’re willing to make the switch to a Windows or OSX core, it should help significantly in alleviating the issue. If you plan on troubleshooting this issue further on Linux and are able to successfully find out where multicast is going wrong, please do let us know as we would love to have more information as to what exactly causes it.
Thanks,
Noris