I think that this is the effect of your instruction
lxc config device set smith-01 lxdbr0 ipv4.address 10.171.234.205
and the MAC address is the one used for your new eth1.
So your container has already an eth0 and it’s trying to create a new one from the dnsmasq dhcp server.
Well, maybe something has changed in the host configuration and was only validated by the reboot and then it’s fighting with the LXD dnsmasq. I’d try to add some tracing to the LXD dnsmasq config by using something like that - see man dnsmasq for the available syntax.