When Roon Support gets to you they will have a more systematic way of trouble shooting your dropout problems. But you can try this:
Technicolor routers are known to cause some issues: https://kb.roonlabs.com/Networking_Best_Practices
The following post discusses disabling the IPV6 firewall in that router. There may also be some multicast settings that have to be changed, but I don’t have any insight on how to modify them.