Local DNS server unavailable through WiFi Network on Archer VR600
I have a network in my house comprised of an Archer VR600 gateway, and a TP-Link Powerline network to extend wifi to different parts of my house. I use PiHole running on a Raspberry Pi in order to provide local DNS and ad filtering. The network is connected together like this:
2.5 GHz and 5GHz radios are enabled on all devices. The 2.4GHz SSIDs are all called "Net" and the 5GHz SSIDs are all called "Net-Fast".
I am able to connect wifi devices to the networks in all locations sucessfully, and roaming works quite well.
The challenge I am having is when devices connect to the Archer VR600 network, they are often unable to resolve DNS or ping the PiHole server. Devices connected to WiFi on the PowerLine devices are able to resolve names via DNS and ping the PiHole server. If I reboot the VR600 this sometimes resolves the issue, but often it does not. I have tried connecting the PiHole to different ports on the VR600 but this makes no difference.
Note that I am using DHCP on the VR600 to assign the IP address and DNS servers to clients. I had initially been using the DHCP server on the PiHole, but experienced a similar problem so I switched to DHCP on the VR600.
I suspect that the routing between the WiFi radios on the VR600 and the wired switching has a bug which causes this. I would expect to see see this issue if AP isolation was enabled, but it is unchecked in Wireless > Advanced settings on the VR600. Nor have I set up any Interface grouping of the LAN ports - it is as default.
I am running the most recent Firmware available on the TP-Link site (0.3.0 0.9.1 v0074.0 Build 200226 RC.65147n).
Has anyone else experienced any issues with communication between WiFi connected clients and wired clients on the VR600?