IPv6 Addresssing Lost - radvd exited for unknown reason

[priller]

2.2-BETA (amd64)
built on Fri Oct 10

Uptime was around 4 days, 8 hours.

For no apparent reason radvd terminated and IPv6 DHCP-PD addressing was lost.

There was no interface reset or Cable Modem reset or loss of signal on DOCSIS side.

I have Gateway Monitoring (apinger) disabled for IPv4 and IPv6.  I have run that way on 2.1.x for several months, due to the loss of IPv6 addressing if there is even a short gateway event.

I assume radvd restarted because it is a service monitored by Service Watchdog.  But that seems kind of pointless since restarting it does not bring back the lost IPv6 addressing.  A WAN interface release/renew did not help, ended up rebooting.

The logs are below.  No other system or external event at the time radvd exited.

Oct 14 21:13:07 radvd[38204]: resuming normal operation
Oct 14 21:13:07 radvd[38204]: attempting to reread config file
Oct 14 21:13:04 radvd[38204]: resuming normal operation
Oct 14 21:13:04 radvd[38204]: attempting to reread config file
Oct 14 21:13:03 radvd[37564]: IPv6 forwarding seems to be disabled, but continuing anyway.
Oct 14 21:13:03 radvd[37564]: IPv6 forwarding setting is: 0, should be 1
Oct 14 21:13:03 radvd[37564]: version 1.9.1 started
Oct 14 21:09:00 radvd[45856]: no auto-selected prefix on interface igb1, disabling advertisements
Oct 14 21:09:00 radvd[45856]: no auto-selected prefix on interface igb0, disabling advertisements
Oct 14 21:09:00 radvd[45856]: version 1.9.1 started
Oct 14 21:08:13 radvd[761]: removing /var/run/radvd.pid
Oct 14 21:08:13 radvd[761]: sending stop adverts
Oct 14 21:08:13 radvd[761]: Exiting, sigterm or sigint received.

–- Logs from Splunk for same time period ---

Oct 14 21:09:00 php: servicewatchdog_cron.php: Service Watchdog detected service radvd stopped. Restarting radvd (Router Advertisement Daemon)
Oct 14 21:08:21 devd: notify_clients: send() failed; dropping unresponsive client
Oct 14 21:08:21 php-fpm[22452]: /rc.newwanip: Creating rrd update script
Oct 14 21:08:18 apinger: No usable targets found, exiting
Oct 14 21:08:18 apinger: Starting Alarm Pinger, apinger(51282)
Oct 14 21:08:17 php-fpm[22452]: /rc.newwanip: ROUTING: setting IPv6 default route to fe80::201:5cff:fe24:9301%igb3
Oct 14 21:08:17 php-fpm[22452]: /rc.newwanip: ROUTING: setting default route to 76.100.xxx.xxx
Oct 14 21:08:17 php-fpm[22452]: /rc.newwanip: rc.newwanip: on (IP address: 76.100.xxx.xxx) (interface: WAN[wan]) (real interface: igb3).
Oct 14 21:08:17 php-fpm[22452]: /rc.newwanip: rc.newwanip: Informational is starting igb3.
Oct 14 21:08:16 rtsold: Starting dhcp6 client for interface wan(igb3)
Oct 14 21:08:16 php-fpm[22452]: /status_interfaces.php: Accept router advertisements on interface igb3
Oct 14 21:08:16 check_reload_status: rc.newwanip starting igb3
Oct 14 21:08:13 php-fpm[99451]: /status_interfaces.php: Clearing states to old gateway 76.100.xxx.xxx.
Oct 14 21:08:13 php-fpm[99451]: /status_interfaces.php: Shutting down Router Advertisment daemon cleanly

Edit: Additional logs added.

[priller]

Additional logs added to original post.