pfSense

We get everything working, start up pingers to ipv4 and ipv6, then reboot pfSense. We expect all connectivity to be restored when pfSense up and running. ip4 connectivity is always restored.

When the RA mode is set to Assisted, ipv6 connectivity is not restored automatically to Linux or Windows clients when the pfSense is rebooted. The following procedure is the simplest and safest way to restore connectivity I've found.

System Routing Gateways
Restart service does not work. This would restart ipv4 service too which is not necessary.
WAN_DHCP6, edit, disable gateway, save, edit, enable gateway, save, apply changes

When the RA mode is set to Managed, ipv6 connectivity is restored automatically to Linux clients but not to Windows clients after rebooting. Linux can be pushed into failing by resetting the interface:

nmcli connection down "Static Connection"; nmcli connection up "Static Connection"

All ipv6 disappear and do not come back until the gateway reset procedure shown above is performed.

This behavior started immediately after the upgrade from 2.3.2-p1. I went onsite and rebuilt the configuration only to be met with identical behavior.

Functionality in use: dual WAN, only one WAN has ipv6, IPSec

Special setting:
System Routing Gateways
WAN_DHCP6
[x] Disable Gateway Monitoring

This must be disabled or ipv6 connectivity isn't restored under many more scenarios.