I had troubles with this for a very long time and I have finally found a solution. My setup is as follows:
ONT Fiber ---> R7000 WAN ---> Switches ---> Everything else including access points and hard wired tv boxes.
Of course, you need to have IGMP enabled in the LAN settings of the R7000 device. However, when you do this, TV cuts out every 5 or so minutes and comes back with channel switch or in about 30 seconds. The problem seems to be with the firmware. I downgraded from version 184.108.40.206 to version V220.127.116.11. This router is the only one in the equation so it will be your DHCP and everything as well - ditch the T3200M completely. My TV has been stable so far. I have not yet tested any other firmware versions. A rule of thumb is to always use the latest firmware because of security updates but... oh well, this works....
You are taking a big risk using the R7000, especially with the old firmware. The security vulnerabilities of the Netgear routers have been in the news lately. Version 18.104.22.168 is supposed to have some security patches but I haven't tried it. My R7000 has been decommissioned for a year now due to Netgear's inability to release stable and secure firmware since version 22.214.171.124.
The T3200M has some limitations but it is much more secure and stable than the R7000.