QUIC failed (connection timeout)
A simple setup of two servers, both running Debian Bookworm with knot 3.3.2 from pkg.labs.nic.cz. First is primary for approx. 10 zones, second is secondary. The zones are being synchronized over QUIC with mutual authentication as described in https://www.knot-dns.cz/docs/3.3/html/configuration.html#mutual-authentication.
Sometimes, the secondary fails to connect to the primary. Either right after being successfully notified from primary, or when refreshing zone at regular intervals. It happens in about 20% of all trials. Both servers have public IPs, no packet loss between them (tcpdump on both sides shows 4 packets in 2 handskahes - S->P,P->S,S->P,P-S in a quick succession, then 1 packet S->P after 5 seconds followed by the following log error message).
secondary knotd[12345]: info: [example.com.] refresh, remote primary, address 192.0.2.1@853, failed (connection timeout)
Is it some kind of synchronization problem of the QUIC protocol? Will you recommend any way of debugging this issue?