MagentaTV IPTV IGMP Proxy Telekom not Working

Hello everyone. It's me again.
I managed to build a Network with my 7362SL running as Modem (VLAN7 tagged) and a Router 4a as Router doing the PPPoE Stuff. Unfortunatly in this Configuration i am not able to establish a IPTV Connection. Neither on my TVHeadend Server nore with VLC and RTP on any device. I strongly assume that i have a BNG Connection, so that i don't have to configure something with VLAN8 like one had to to in former Entertain days.

Right now i run my Xiaomit 4A (with DHCP) as an Accesspoint behind an 7560. In this configuration IPTV works. But this is not my desired Setup because I want the Xiaomi Router with OpenWRT for VLAN Configuration and Routing,

I tried installing IGMPProxy and config a lot of IP's for the Altnet. Also enabled igmp_snooping on the Lan Interface of the Xiaomi OpenWRT.

Anyone with advices for me?

UPDATE:

Setting up (an other) 7362 with openwrt and using is sucessfull.

opkg update
opkg install igmpproxy
uci set igmpproxy.@phyint[0].altnet=87.141.128.0/17
uci set igmpproxy.@phyint[1].altnet=192.168.178.0/24
uci commit
reboot && exit

Only Problem seems to be, that the 7362 is not powerful enough for Routing so 2 parralel streams are not running.

Problem with the 4a seems to be that igmp snooping is kind of not working or i am not unterstanding how to Set it up.

Maybe Finding a powerfull openwrt device will help me.