I wanted to use the IPv6 DHCP server to hand out addresses for other subnets
It wont let you add scopes that are not part of the Lan IP, So I used a /48
and then used /64 for the scopes
After I saved it, the web interface was no longer accessable
though I could ping the routers IPv4 and IPv6 addresses
I can NOT access the web interface, and had to reset to factory defaults to get it working again