IPv6 not working on OpenWRT 23.05.2 in AP mode (IPv6 address is being assigned)

Hi,

I'm running OpenWrt 23.05.2 (r23630-842932a63d) on a TP Link Archer C7 v2.
I've managed to set up OpenWRT as a 'dumb' AP, with VLANs, WiFi 802.11x and WiFi. My OpenWrt is running behind a OPNSense core router.

If I connect directly to the OPNSense core router all is well, and both IPv4 and IPv6 are working (I've verified this with ping and tracert under Windows)//

My OpenWrt AP is getting a valid external IPv6 IP address on VLAN 128 (labeled NETW):

# ip address show br-netw
9: br-netw: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether 30:b5:c2:dd:51:26 brd ff:ff:ff:ff:ff:ff
    inet 172.17.2.1/16 brd 172.17.255.255 scope global br-netw
       valid_lft forever preferred_lft forever
    inet6 2a02:a46b:487c:c010::1bb8/128 scope global dynamic noprefixroute
       valid_lft 6505sec preferred_lft 3805sec
    inet6 fe80::32b5:c2ff:fedd:5126/64 scope link
       valid_lft forever preferred_lft forever

Switch settings for VLAN 128 are:

network.switch_netw=switch_vlan
network.switch_netw.device='switch0'
network.switch_netw.vlan='128'
network.switch_netw.description='NETW'
network.switch_netw.ports='0t 1t 2t'

Interface settings for VLAN 128 are:

# uci show network.netw
network.netw=interface
network.netw.device='br-netw'
network.netw.proto='dhcp'

# uci show network.netw6
network.netw6=interface
network.netw6.device='@netw'
network.netw6.proto='dhcpv6'
network.netw6.reqaddress='try'
network.netw6.reqprefix='auto'
network.netw6.delegate='0'

# uci show network.br_netw
network.br_netw=device
network.br_netw.name='br-netw'
network.br_netw.type='bridge'
network.br_netw.ports='eth1.128'

Pinging does work from the OpenWRT AP does work with IPv4 but not with IPv6:

# ping -c 4 -4 google.com
PING google.com (172.217.23.206): 56 data bytes
64 bytes from 172.217.23.206: seq=0 ttl=117 time=4.376 ms
64 bytes from 172.217.23.206: seq=1 ttl=117 time=4.402 ms
64 bytes from 172.217.23.206: seq=2 ttl=117 time=4.434 ms
64 bytes from 172.217.23.206: seq=3 ttl=117 time=4.391 ms

--- google.com ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 4.376/4.400/4.434 ms

# ping -c 4 -6 google.com
PING google.com (2a00:1450:400e:802::200e): 56 data bytes

--- google.com ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss

Debugging the route using traceroute doesn't lead to usable results:

# traceroute -6 -m 16 google.com
traceroute to google.com (2a00:1450:400e:802::200e), 16 hops max, 72 byte packets
 1  *  *  *
 2  *  *  *
 3  *  *  *
 4  *  *  *
 5  *  *  *
 6  *  *  *
 7  *  *  *
 8  *  *  *
 9  *  *  *
10  *  *  *
11  *  *  *
12  *  *  *
13  *  *  *
14  *  *  *
15  *  *  *
16  *  *  *

What would be a good way to proceed to see what is going wrong and to solve the problem?

Thanks,
Joost

I've also tried to use the command ifstatus and that gives the following results...

# ifstatus netw
{
        "up": true,
        "pending": false,
        "available": true,
        "autostart": true,
        "dynamic": false,
        "uptime": 37980,
        "l3_device": "br-netw",
        "proto": "dhcp",
        "device": "br-netw",
        "metric": 0,
        "dns_metric": 0,
        "delegation": true,
        "ipv4-address": [
                {
                        "address": "172.17.2.1",
                        "mask": 16
                }
        ],
        "ipv6-address": [

        ],
        "ipv6-prefix": [

        ],
        "ipv6-prefix-assignment": [

        ],
        "route": [
                {
                        "target": "0.0.0.0",
                        "mask": 0,
                        "nexthop": "172.17.0.1",
                        "source": "172.17.2.1/32"
                }
        ],
        "dns-server": [
                "172.17.0.1"
        ],
        "dns-search": [
                "netw.locallan"
        ],
        "neighbors": [

        ],
        "inactive": {
                "ipv4-address": [

                ],
                "ipv6-address": [

                ],
                "route": [

                ],
                "dns-server": [

                ],
                "dns-search": [

                ],
                "neighbors": [

                ]
        },
        "data": {
                "dhcpserver": "172.17.0.1",
                "hostname": "wap-joost.netw.locallan",
                "leasetime": 4000,
                "ntpserver": "172.17.0.1"
        }
}

# ifstatus netw6
{
        "up": true,
        "pending": false,
        "available": true,
        "autostart": true,
        "dynamic": false,
        "uptime": 4007,
        "l3_device": "br-netw",
        "proto": "dhcpv6",
        "device": "br-netw",
        "metric": 0,
        "dns_metric": 0,
        "delegation": false,
        "ipv4-address": [

        ],
        "ipv6-address": [
                {
                        "address": "2a02:a46b:695b:c010::1bb8",
                        "mask": 128,
                        "preferred": 2742,
                        "valid": 5442
                }
        ],
        "ipv6-prefix": [
                {
                        "address": "2a02:a46b:695b:c0f0::",
                        "mask": 62,
                        "preferred": 2742,
                        "valid": 5442,
                        "class": "netw6",
                        "assigned": {

                        }
                }
        ],
        "ipv6-prefix-assignment": [

        ],
        "route": [
                {
                        "target": "2a02:a46b:695b:c000::",
                        "mask": 58,
                        "nexthop": "::",
                        "metric": 256,
                        "valid": 86277,
                        "source": "::/0"
                },
                {
                        "target": "::",
                        "mask": 0,
                        "nexthop": "fe80::2f1:f3ff:fe1f:898b",
                        "metric": 512,
                        "valid": 1677,
                        "source": "2a02:a46b:695b:c0f0::/62"
                },
                {
                        "target": "::",
                        "mask": 0,
                        "nexthop": "fe80::2f1:f3ff:fe1f:898b",
                        "metric": 512,
                        "valid": 1677,
                        "source": "2a02:a46b:695b:c010::1bb8/128"
                }
        ],
        "dns-server": [
                "2a02:a46b:695b:c010:2f1:f3ff:fe1f:898b"
        ],
        "dns-search": [
                "netw.locallan"
        ],
        "neighbors": [

        ],
        "inactive": {
                "ipv4-address": [

                ],
                "ipv6-address": [

                ],
                "route": [

                ],
                "dns-server": [

                ],
                "dns-search": [

                ],
                "neighbors": [

                ]
        },
        "data": {
                "passthru": "001700102a02a46b695bc01002f1f3fffe1f898b0018000f046e657477086c6f63616c6c616e00"
        }
}