'djbdns cache doing huge amount of query on dns root server

I know this could be a bottle in the sea but.

I've settle an internal DNS using Tinydns (let's call it vmDNS) that have been working for while now. Yesterday very strange behavior that I cannot explain. I had huge amount of query to Root DNS server coming from my vmDNS around 50 per second.

I may have missed something here but why my vmDNS is supposed to ask to DNS resolution to root server as I've configured the resolver to ask 8.8.8.8.

In the mean time looking at the process running and filtering on "dns" value it appears I have hundred of dnscache process running. I've killed thoses process and so far it came back to normal.

But I cannot understand why this happened.

Note: The vmDNS is not reachable from outside the network.

Here some command output while the strange behavior was happening.

 ps -aux |grep dns
    dnscache  14811 dnscache  189u  IPv4 669392975      0t0  UDP vmDNS:8460->192.203.230.10:domain 
dnscache  14811 dnscache  190u  IPv4 669389015      0t0  UDP vmDNS:30047->192.5.5.241:domain 
dnscache  14811 dnscache  191u  IPv4 669392974      0t0  UDP vmDNS:34153->192.203.230.10:domain 
dnscache  14811 dnscache  192u  IPv4 669376088      0t0  UDP vmDNS:45196->128.9.0.107:domain 
dnscache  14811 dnscache  202u  IPv4 669393005      0t0  UDP vmDNS:37691->198.41.0.10:domain 
dnscache  14811 dnscache  203u  IPv4 669393015      0t0  UDP vmDNS:40394->192.112.36.4:domain 
-------------------------------
dnscache  14811 dnscache  171u  IPv4 669389086      0t0  UDP vmDNS:45861->198.32.64.12:domain 
dnscache  14811 dnscache  172u  IPv4 669389087      0t0  UDP vmDNS:57794->198.41.0.4:domain 
dnscache  14811 dnscache  173u  IPv4 669389088      0t0  UDP vmDNS:62378->128.8.10.90:domai
linuxdnsdebian-buster


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