Homekit accessories went offline or "non response" frequently.
Previously this issue was reported.
There is a possibility that multiple hub-capable devices are confusing all the accessories, especially when the internet subnet setting is complicated. Even the HomePod will track your iPhone network location and tried to signing the same network, even tho it is different from apple tv, then apple tv will lose the audio output to HomePod.
My HomeKit accessories included some bluetooth-transmission product, and they went offline so frequently that makes it suspicious that ppl are hacking into home router, etc.
After that, i tried to ban the HomePod from all routers except one that work with apple TV. Besides, i reboot apple TV 1-2 times day, followed by all sequential reboot of the rest "standby" hubs, so they cannot usurp the "acting" hub status.
So far it has been working smoothly without disconnection except the time of reboot. I use multiple bluetooth-controlled smart plugs to schedule turn-off and turn-on time for every single "hub" capable devices.