It appears .au zone has DNSSEC issues which is causing domains to be unresolvable by many resolvers. The .au DNS zone is not controlled by us unfortunately so we are not able to fix this.
RRSIG com.au/DS alg 8, id 62233: The Signature Expiration field of the RRSIG RR (2023-09-18 00:05:29+00:00) is 17 minutes in the past.
We have made our resolvers ignore the DNSSEC for .au domains temporarily while the issue is ongoing to alleviate the issue as much as possible.