"Server failure" on DNS resolver (TLV)

I’ve been using as a DNS resolver for all devices at home (no forwarder in-between), and today I’ve experienced occasional resolver errors. Specifically, at sporadic times queries (even popular, probably-cached entries like A www.twitch.tv) will just fail with “server failure” (reply code 2). Retrying it a couple seconds later will work, and it’s usually a batch of requests (sent at that same second) that fails rather than just one.

This is happening on the TLV node, so the issue might be isolated to it. [debug information]