Specific answers require specific questions. When in doubt, post the output of "/ip address print detail", "/ip route print detail", "/interface print detail", "/ip firewall export", and an accurate network diagram.
and afterwards have problems when you have to choose - ipv4 multicast with iptv subscribers or ipv6 network working. That is, if you imply to use igmp snooping. Or less disastrous - what to do when you need features from IGMPv3.