I returned to the previous records, what do I do now, because the error persists?
The only problem I could find was the setup of afraid.org. Though ns{1..4}.afraid.org have AAAA records, the authoritative DNS servers for afraid.org are IPv4 only. However that shouldn't be a problem for this step of the certification. It will however become a problem for a later step of the certification.
So, I don't know why the current step is failing for you. It might be that records are cached on a DNS server somewhere, and you have to wait for the cache to expire. The largest TTL I noticed was 48 hours. Assuming you haven't used higher TTL values than that, then all the old records will expire if you wait until 48 hours after your last DNS change.
If waiting doesn't solve the problem, then there must be something else wrong.