Problem with IGMP (possible bug)

[fess]

Hello! Thanks Merlin for this firmware! I
I have asus ac68u but this is problem with IGMP.
Short description:
IPTV goes to me by dedicated ethernet cord. I connected it to LAN4 of my router.
Then I create VLAN3 for it and make next setup:
nat-start script:

# lan ports 1-3 assigned to vlan1
robocfg vlan 1 ports "1 2 3 8t"
# port 4 to vlan3
robocfg vlan 3 ports "4 8t"
vconfig add eth0 3
ifconfig vlan3 192.168.2.1 up

#static route for IPTV
echo "2" > /proc/sys/net/ipv4/conf/all/force_igmp_version
iptables -I INPUT 1 -i vlan3 -j ACCEPT
route add -net 212.48.196.0/24 dev vlan3
route add -net 78.36.1.0/24 dev vlan3
route add -net 224.0.0.0/4 dev vlan3

#run udpxy and xupnpd (installed from entware)
/opt/bin/udpxy -p 4000 -m 192.168.2.1 -c 6  -B 1Mb  -R 100
/opt/bin/xupnpd

After it IPTV is working but it turns off every 270 sec.
tcpdump shows:

22:18:40.021946 IP 192.168.2.1 > 233.26.198.120: igmp v2 report 233.26.198.120
22:18:47.491899 IP 192.168.2.1 > 233.26.198.120: igmp v2 report 233.26.198.120
22:18:54.441901 IP 192.168.2.1 > 233.26.198.120: igmp v2 report 233.26.198.120
22:19:17.415659 IP 192.168.1.1 > 224.0.0.1: igmp query v2
22:19:17.415900 IP 192.168.1.1 > 224.0.0.1: igmp query v2
22:21:24.263067 IP 192.168.1.1 > 224.0.0.1: igmp query v2
22:21:24.263185 IP 192.168.1.1 > 224.0.0.1: igmp query v2
22:22:00.002142 IP 192.168.2.1 > 224.0.0.2: igmp leave 233.26.198.120

If I install dd-wrt firmware (with the same config) iptv shows normal:

21:41:29.860425 IP 192.168.1.1 > 224.0.0.1: igmp query v2
21:41:29.860700 IP 192.168.1.1 > 224.0.0.1: igmp query v2
21:41:33.070600 IP 192.168.2.1 > 233.26.198.49: igmp v2 report 233.26.198.49
21:41:33.903516 IP 192.168.2.1 > 233.26.198.10: igmp v2 report 233.26.198.10

As you can see there is no answer (report) to igmp query in Asuswrt-Merlin. I think this is the bug. It is possible to fix it?
Maybe I made some errors in this config?
dd-wrt has very low WAN<->LAN (about 150 Mbit). On this firmware I have more than 350 Mbit.