It’s been stable for a few days now, running on the headless Mac mini. Has anything changed at Roon as nothing has changed here - for example, does Roon auto update software?
I have ordered a new router to replace the BT Home Hub (although this brings it’s own problems as using a non BT router means I will lose my home landline phone, if you can believe it!) and I will wire the Mac Mini direct to the new router.