In https://github.com/vyos/vyos-1x/blob/rolling/src/system/on-dhcpv6-event.sh#L72 lease_addr is never defined in the for loop. Should be lease_ip.
Current code gives log messages showing only the prefix, not the ip/prefix combi
Jul 13 09:48:55 vyos1 on-dhcpv6-event[4141]: Processing PD route for /64. Link local: fe80::215:5dff:fe20:96 ifname: eth0 Jul 13 09:48:55 vyos1 kea-dhcp6[4141]: <13>Jul 13 09:48:55 on-dhcpv6-event: Processing PD route for /64. Link local: fe80::215:5dff:fe20:96 ifname: eth0 Jul 13 10:26:25 vyos1 on-dhcpv6-event: Processing PD route for /64. Link local: fe80::215:5dff:fe20:96 ifname: eth0 Jul 13 10:26:25 vyos1 kea-dhcp6[7061]: <13>Jul 13 10:26:25 on-dhcpv6-event: Processing PD route for /64. Link local: fe80::215:5dff:fe20:96 ifname: eth0