A network can quickly get complicated. Can a simpler setup help SQ? It might, it might not. That CA (Romaz) 'direct' connection of the rendu to the server/player is an example that did help in my setup:- PC-->rendu-->DAC-V1.
If you are clever at IT (which I am not), you might be able to get this rendu 'direct' connection some other way. The rendu uses the Sonore web GUI for configuration so either way it will need to connect to the internet for that, at least initially.
The method as described at CA is what I (cleverly) followed. It requires my PC to have a second ethernet port for the rendu and a 'bridge' via the OS to connect it to my existing LAN (with the DHCP server/router). That thread now has pointers on the first page for a few different OSs.
I only have one network interface port so I use a USB/Ethernet adapter to provide the second port (in place of a second NIC). I have one adapter by Anker (on the Win 7 64 bit PC) and another by Apple (on a Win 10 64 bit laptop). The Apple one needs a Win 10 64bit driver which I downloaded from the asix website (AX88772A) after a little google search.
The effort was worthwhile for me and I am grateful to the OP.