I notice in my PiHole DNS logs that I have thousands of requests from my M9 units to the following DNS root server, a.root-servers.net

Is this normal and expected behaviour, or is the device in some non ideal configuration to cause this behaviour?

On my LAN I assign a DNS server IP via DHCP which points to y PiHole server for filtering. My local domain is passed to another internal DNS server and all external requests are sent on to CloudFlare if not already in the PiHole cache. A reasonably standard setup.

Thanks in advance,

Phill