Can you share the topology information? Do we know if all the devices are connected with a single unmanaged switch? Also the deco mesh system is also connected with same unmanaged switch? Sometimes creating a single large Broad case domains specially in case where you have a lot of media devices isn't good. Would suggest you to separate the networks so that is TV / media gets busy it wouldn't impact wifi. Also gives you additional controls on security as you might not want users on wifi to access management or any other service running on different vlan which can be done via access controls.