Do you have IGMP-SNOOPING enabled? There was a bug with igmp-snooping previously in the 10.x train (can't remember the exact code revision) that caused 224.0.0.x/24 igmp groups to not be flooded as they should be.
If its enabled, try disabling igmp-snooping "deactivate protocols igmp-snooping' and see if they helps out.