Thanks; I believe I know what happened in this case and we’ll be improving the heuristic to avoid it.
But people without working IPv6 should better get their resolver configured not to use IPv6. You won’t need to wait for this fix to avoid the case and even generally that configuration should slightly improve latency, etc. From my point of view the ideal way of doing this (with recent-ish Turris OS) is to set IPv6 to disabled in the GUI /reforis/network-settings/wan.
From DNS server’s point of view the detection isn’t so easy. Individual server might not respond, or there might be some kind of a short outage somewhere on the way (specific to IPv6 or not), or perhaps your network hasn’t fully started up yet, etc.