2.4g devices become non responsive once switch home hub to 5g

Using Netgear Router RS600 that broadcasts a 2.4ghz and 5ghz wifi signal separately. Would love to use smart connect feature and broadcast them all under one SSID and use the 6g for new iPhone but haven't been able to add any 2.4g homekit devices doing it that way.

So I separated the two signals. Have switch bot curtain and blind tilt devices and Nanoleaf shapes and elements added to homekit by joining 2.4g wifi on my iPhone. I also had to switch my Apple TV 4K to the 2.4g wifi. Homekit would not add them if any of my home hubs were connected to 5g....strange. Then I was able to successfully add these devices to homekit. BUT....when I switch my Apple TV and iPhone 16 back to my 5g Wifi, those devices become non responsive within homekit. They work fine in their native app under 5g.

I had no issues before...for the last year in fact nothing changed in my setup, until I got my new iPhone 16 and I had "ghost" homes showing up and Apple support had me delete the home app and reinstall it. Thus I had to recreate my home ecosystem. This is where there were issues.

Any idea? Is this a TV OS issue? IOS 18 issue?

Funny thing is, I have a HomePod mini that I kept on the 2.4g wifi signal, and thank god for the new homekit update that allows us to choose which home hub to act of primary hub. When I select the HomePod mini (that uses the 2.4g signal), these devices become responsive and work.

This problem didn't exist until this update. Am I doing something wrong? Any ideas? I know I can just keep the HomePod as the hub and will be fine.