NPTv6 seems to not work, due to an ip6tables syntax.
set nat nptv6 rule 10 source prefix 2001:db8:ffff:ffff::/64 set nat nptv6 rule 10 outbound-interface eth0 set nat nptv6 rule 10 translation prefix 2001:db8:1111:1111::1/64
vyos@office01-lon01# commit [ nat nptv6 ] ip6tables: Invalid argument. Run `dmesg' for more information. [[nat]] failed Commit failed