Things improve! I have just uninstalled Norton Ultra to replace it with the windows 10 builtins; previous experience has made this seem hard and risky. Hopefully not now it would seem.
Swapping Norton Ultra for Windows Defender and Firewall on Windows 10.
Use “Add and remove programs” to uninstall Norton Ultra; windows offers to turn on Defender, it will update the signature file and your off. You are advised to reboot.