Unbound stops forwarding for a domain

[random1104]

Hello!,

I have a "domain override" pointing to internal authoritative servers, one domain pointing at a list of IPv4 and IPv6 IPs.

It works for some time, and then it stops forwarding to the internal servers and the resolution seems to go all the way to the root servers in Internet. After restarting the unbound service it starts working again, which is weird since I would expect a SERVFAIL if there's a temporary issue, not NXDOMAIN from root servers.

No errors present in the logs, so I cannot tell there's a bug or misconfiguration on my side. Any pointers on how to debug this?