This was a bit of a head scratcher. I don’t run DHCP on my home network because I use VNC to admin things from the main machine. This means keeping an IP list, which is easy.
After rebuilding a machine, whenever I set the TCP settings, the router IP would be lost. Everything else would retain ok, but the default gateway constantly reset itself to blank.
The fix, after much research was to reset the TCP/IP stuff from a command prompt by typing:
netsh int ip reset
lovely
