Why does IPTV multicast disappear after a while?

Question

Mikrotik

Created a radio bridge from: SXT HG5 (RBSXTG-5HPnD-HGr2) and Light Head Grid (LHG 5)
Mode - transparent bridge. At one end it is connected to the output of the FTTB switch port, at the other end - an IPTV set-top box from Rostelecom.
When you connect the set-top box directly to the port - it shows flawlessly, when using the radio bridge - the broadcast stops after about 1-3 minutes, the picture freezes.
If you use rewind (as I understand it, the mode changes to unicast and the stream format changes to HLS), - rewind a little back, then everything works fine.
I enclose the configuration, the setting is minimal, enabled multicast-helper=full
I did not install IGMP proxy, because a transparent bridge is required. At the other end is a camera (also from Rostelecom) and sends the flow in the opposite direction. Camera works.
As I understand it, the set-top box should periodically send some kind of packet to the broadcast server, that it is live and the channel is being watched, but how to do this?

Configuration

# oct/22/2018 15:16:04 by RouterOS 6.43.4
# software id = TDDB-5LU8
# model = RouterBOARD LHG 5nD
# serial number = 6FххххB81067
/interface bridge
add fast-forward=no igmp-snooping=yes name=bridge1
/interface wireless
set [ find default-name=wlan1 ] band=5ghz-onlyn channel-width=20/40mhz-XX \
    disabled=no frequency=auto frequency-mode=superchannel mode=\
    station-bridge multicast-helper=full nv2-preshared-key=хххqBff2M \
    nv2-security=enabled radio-name=ASAD_st ssid=ASAD_br_AP \
    wireless-protocol=nv2
/interface ethernet
set [ find default-name=ether1 ] advertise=\
    10M-half,10M-full,100M-half,100M-full,1000M-half,1000M-full
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip hotspot profile
set [ find default=yes ] html-directory=flash/hotspot
/interface bridge port
add bridge=bridge1 hw=no interface=ether1
add bridge=bridge1 interface=wlan1
/ip service
set telnet disabled=yes
set ftp disabled=yes
set www disabled=yes
set ssh disabled=yes
set api disabled=yes
set api-ssl disabled=yes
/system clock
set time-zone-name=Europe/Moscow
/system routerboard settings
set silent-boot=no

Answer 1

Decided to make things easier. I took a Mikrotik haplite, reset the configuration, installed ports 3 and 4 in the bridge. Port 3 inserted into the FTTB switch, port 4 - into the set-top box. The picture and the dump are still the same, the picture gets up in about a minute. After switching channels, the broadcast continues safely.
I re-read "Networks for the smallest. Part nine. Multicast" on Habré. I found an article with information that is not in "networks for small ones" - "Optimizing the transmission of multicast traffic on a local network using IGMP snooping" on the same hub.
Disabled IGMP snooping, assigned bridge1 mac address manually (non-existent), disabled STP, and in the settings of all ports in the bridge, unchecked the boxes as in the screenshot. Everything worked.
Thank you all for participating!

Answer 2

igmp is not working for you