IPv6 Default gateway uses parent nic of PPPOE interface
WAN - IPv4 PPPoE via re1, IPv6 via SLAAC.
Expected result: Stable IPv6 connectivity
When booting, pfsense brings up PPPoE wan, using pppoe1.
ipv6 RA is recieved from ISP.
IPv6 Default gateway is then set to fe80::f2f7:55ff:fe55:d300%re1
The problem here is the %re1 - this is the parent interface, and not the PPPoE link.
While this is in use as default gateway, there is no WAN or LAN ipv6 connectivity.
SSH to pfsense
route del -inet6 default
route add -inet6 default fe80::f2f7:55ff:fe55:d300%pppoe1
This solution is only temporary until either a new RA is recieved, or the system reboots, or the PPPoE link reconnects.
This has happened since around 2.2 era, on all types of hardware.