Regular prompts from Defender Firewall about OneDriveFile Co-authoring

MS resolved it. It turns out that the rule was no active in the public profile and occasionally I was losing Lam connectivity and switching temporarily to WiFI. had I ever left the building in the last 6 months I suppose I would have worked it out - but as the LAN came back on pretty quickly the issue would go away -on its own and hence the very intermittent nature (and the lack of anyone else with the same issue).