My params:
RB450G FW 3.10 SW 6.13
Trying to add a IPv6-address of DNS server - I can add it to IP-DNS only. It works here, but when I open the Quick Set window, I can see an error: A DNS address cannot be of 0.0.0.0, and there is one such address (0.0.0.0) for each IPv6 address entered in IP-DNS window. These addresses remain as the errorneous ones in the Quick Set window, and it is impossible to delete them from that window.
You can always reproduce this behaviour, as far as I know.
Best Regards,