The earliest recollection of this bug is traced back to PAN-OS 8.1.11 - January 09, 2024. This bug is fixed in PAN-OS versions 8.1.11. An enhancement was made to enable you to configure IPv6 in the web interface and through a CLI command when you added IPv6 virtual addresses to a firewall in a high availability (HA) active/active configuration. For more information: https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-release-notes/pan-os-8-1-addressed-issues/pan-os-8-1-11-addressed-issues