My TV Box was experiencing several freezes and the tech support told me it could be due to IGMP multicast flooding in the network. They recommended to turn on IGMP-Snooping in my switches/routers in order to minimize unneeded multicasts.
While there was a native option in my TL-SG108E switches I couldn't find it in my OpenWRT router, so I installed igmpproxy.
However, after double-checking, the IGMP Snooping option is available after all (Network --> Interfaces --> Physical Settings), even without the igmpproxy binary.
Since this is IGMP snooping is the only thing I needed, I uninstalled igmpproxy and the messages didn't appear anymore.
Thank you all