No more ipv6 in container

Hello, I have some troubles with dnsmasq and ip6.

All the containers lost ipv6 address, my syslog is full of:
dnsmasq-dhcp: no address range available for DHCPv6 request via lxdbr0

Just after a reboot the ipv6 are correctly assigned, but after a while they disappear.

I’m on Ubuntu 18.04, with lxc/lxd 3.12 (snap)

Someone have similar problems?

I think the problem it’s releted to this configuration file:
/etc/systemd/network/ (link)

Maybe add ipv6 address to may help, I need to test it…