Probably a major issue that prevented this router from being safely usable on an IPv6 connection - until now. There is now an IPv6 firewall configurable under Firewall -> IPv6 Firewall. By default this new firewall will be ENABLED. That means if you previously relied on the fact that there was no firewall on the IPv6 network to allow remote access to computers on your LAN, you will now have to configure the appropriate firewall rules on that new tab.
Bear in mind that this is quite different from what you are used with IPv4. In IPv4, by default no device is reachable because of NAT. You have to open a port, which will allow connection on your router IPv4 to be forwarded to the selected computer.
With IPv6, every device on your network gets its own, fully routable IPv6. Instead of forwarding ports, you will be opening ports in the firewall, specifying the IPv6 IP of the target computer. That also means that, when connecting (or testing with a port scanner) to that open port, you have to use the computer's IP, not the WAN IP.