erl ipv6 not working for some addresses

I have just found out that my ISP is offering ipv6 ranges, and so am attempting to enable it for my erl (v1.8.0).

Initially, it appeared to be working correctly, as I could access https://ipv6.google.com/ and http://test-ipv6.com/ with no issues, however when I tried out more ipv6 sites, most time out making ipv6 unusable.

If I do a wget on the erl, then it can load the pages successfully, however the same does not apply to any of the machines i tested on my network. I am completly lost as to what the issue could be, seeing as it is only some websites/ip addresses that appear to not be being forwarded by the erl.

Does anyone have any suggestions to solve my issue?

Below is the relevent portions of my config

firewall {
    all-ping enable
    broadcast-ping disable
    group {
    }
    ipv6-receive-redirects disable
    ipv6-src-route disable
    ip-src-route disable
    log-martians enable
    options {
        mss-clamp {
            mss 1412
        }
    }
    receive-redirects disable
    send-redirects enable
    source-validation disable
    syn-cookies enable
}
interfaces {
    ethernet eth0 {
        address 10.42.13.254/24
        description Local
        duplex auto
        speed auto
        vif 250 {
            address 10.42.250.254/24
            description Poltergeist
        }
    }
    ethernet eth2 {
        address dhcp
        description Modem
        dhcp-options {
            default-route no-update
            default-route-distance 210
            name-server no-update
        }
        duplex auto
        pppoe 0 {
            default-route auto
            dhcpv6-pd {
                pd 0 {
                    interface eth0 {
                        host-address ::1
                        prefix-id D
                        service slaac
                    }
                    prefix-length 56
                }
                rapid-commit enable
            }
            firewall {
                in {
                    name WAN_IN
                }
                local {
                    name WAN_LOCAL
                }
                out {
                    name WAN_OUT
                }
            }
            ipv6 {
                dup-addr-detect-transmits 1
                enable {
                }
            }
            mtu 1492
            name-server auto
        }
        speed auto
    }
    loopback lo {
    }
}
protocols {
    static {
        interface-route6 ::/0 {
            next-hop-interface pppoe0 {
            }
            next-hop-interface tun0 {
            }
        }
    }
}
service {
    dhcp-server {
    }
    dns {
        forwarding {
            cache-size 150
            listen-on eth0
            listen-on eth1
            listen-on eth1.1
            listen-on eth0.250
            listen-on vtun0
            listen-on eth2.6
        }
    }
    gui {
        https-port 443
    }
    nat {
        rule 5010 {
            log disable
            outbound-interface pppoe0
            protocol all
            type masquerade
        }
    }
    ssh {
        port 2299
        protocol-version v2
    }
}
system {
    name-server 8.8.8.8
    name-server 8.8.4.4
    name-server 2001:4860:4860::8888
    name-server 2001:4860:4860::8844
    offload {
        ipv4 {
            vlan enable
        }
        ipv6 {
            forwarding enable
        }
    }
    time-zone UTC
    traffic-analysis {
        dpi enable
        export enable
    }
}