When I try to forward port 53/tcp and port 53/udp to a container, it triggers the duplicate port protections. Is this a known bug, and is there a workaround? 

/usr/bin/docker: Error response from daemon: driver failed programming external connectivity on endpoint bind (b02afe12d7e2bd9ea08cae7ad3bdeecab9609f8278418a8fb71f9a1ad042c6b1): Error starting userland proxy: listen tcp 0.0.0.0:53: bind: address already in use.

Probably because port 53 tcp is already in use to handle DNS requests from the container itself to the host system.

unRAID runs dnsmasq which is already listening/using port 53.