OSX & IP networking problems? [Solved]

This is doing my head in! I don’t think its particularly a Roon issue but this where the problems show up. The main problem i now have is my Meridian ID 40 zone that appears after rebooting Roon but drops after playing for about 5 seconds?
My setup is running Roon (not server) on Mac Mini 2010 intel - 8Gb ram that serves as my home hub, mainly serving Plex & Roon with data coming from a 2Tb NAS. Zones are Meridian ID40 & MC200 ethernet wired to a Netgear GS116Ev2 switch that also feeds the Mac Mini, the NAS, Apple tv4, Sky etc.
The router is currently the BT Home Hub 5 that has 4 gigabit ports but this is changing next week for the Sky Q router that only has two ethernet ports.
Wi-fi connections are various iPads & iPhones, smart TV’s and games consoles a couple of Airport Express and various AirPlay devices.
After the 1.2 update i had some issues with the wi-fi zones not appearing but this seems to be solved with the build 128. The GS116 switch was a new purchase to allow all the ethernet feeds to be run to the one switch in case the problem was down to some feeds going to my old 8 port switch and some to the BT router.
Any ideas?

Where is Roon core running if not on the Mac mini?

Sorry if not clear. The Roon core is running on the Mac Mini but I’m running the full Roon not the Roon Server.

After lots more tests it appears that the issue is one of Sooloos not releasing the ID40 properly while the MC200 is powered as after powering the MC200 off and giving the 861/ID40 a hard power off/on rather than just standby off/on the ID40 zone reappears and stays on.
The strange bit is that the ID40 zone was showing and starting to play in Roon but dropping the audio and dissapearing from the seup after just a few seconds. All the M kit is running the latest build updates and was happily playing Roon or Sooloos before 1.2, dropping the Sooloos hold every time I asked for the Roon ID40 zone from standby.

Finally solved this. It was a ‘multicast’ issue solved by activating the multicast querier option buried in the router settings.