I lose ipv6 after a few minutes

[Hoerli1337]

Describe the bug

My ISP provides a /56 prefix over IPv6.
I have a PPPoE connection (FTTH connection).
I also get an IPv6 assigned without any problems when I start OPNsense.
My computer also gets an IPv6 assigned.
Up to here everything is fine.
I only get an IP address assigned via interface logging if I create a WAN rule that allows port 547 -> 546.
I found this hint in the internet.
()

After about 2-3 minutes, the connection drops for all IPv6 packets.
If I restart the firewall or reboot my PC, I can connect to the internet again via IPv6 for 2-3 minutes.
Both devices still have an IPv6 address assigned.
OPNsense also has an address for the LAN and WAN interface.

Only now comes the strange thing, if I execute a ping command, the result looks like this:
PC -> OPNsense LAN interface = OK
PC -> OPNsense WAN interface = Not ok
PC -> WAN address = Not ok
OPNsense WAN -> WAN address = OK (Ping tool in the web interface)
OPNsense LAN -> WAN address = OK (Ping tool in the web interface)

As it looks, OPNsense suddenly starts dropping the packets.
For whatever reason.
I have a rule for IPv4 and IPv6 each, which is structured as follows:
LAN -> WAN | IPv4 / IPv6 | any -> any

Environment

Software version used and hardware type if relevant, e.g.:

OPNsense 21.1.6-amd64 (amd64, OpenSSL)
FreeBSD 12.1-RELEASE-p126-HBSD
OpenSSL 1.1.1k
Intel® Core i5-10500T
RAM: 2x 4GB
Network Intel® X550-T2 (WAN + LAN)
Network 2: Intel I219-V (OnBoard-LAN)

I created this issue here because there seems to be another person who has the same problem on the OPNsense forum, but there is no solution to it yet:
https://forum.opnsense.org/index.php?topic=22052.0

[OPNsense-bot]

Thank you for creating an issue.
Since the ticket doesn't seem to be using one of our templates, we're marking this issue as low priority until further notice.

For more information about the policies for this repository,
please read https://github.com/opnsense/core/blob/master/CONTRIBUTING.md for further details.

The easiest option to gain traction is to close this ticket and open a new one using one of our templates.

[sourcenux]

Could you check if the opnsense blocks any ICMP(v6) traffic? ( Firewall > Log Files > Live View )

[OPNsense-bot]

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