I have seen this multiple times, that on running shuffledns twice I get different results, and the results does not vary by 2-5 domains but in huge numbers. This huge difference come only in first and second run.
$ cat altdns.txt| shuffledns -silent -d domain -r ips/resolvers.txt | tee a.txt
$ cat a.txt | wc -l
619
$ cat a.txt| shuffledns -silent -d domain -ips/resolvers.txt | wc -l
95
Resolvers are taken from dnsvalidator.
Strangely, if I pass the same subdomain to shuffledns it does not output as it should be:
I have observed this issue for other domains also.
dig tr.recorder.example.com
; <<>> DiG 9.11.5-P4-5.1ubuntu2.2-Ubuntu <<>> tr.recorder.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 17767
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;tr.recorder.example.com. IN A
;; AUTHORITY SECTION:
example.com. 900 IN SOA ns-546.awsdns-04.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
;; Query time: 113 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Tue Jun 23 07:34:29 UTC 2020
;; MSG SIZE rcvd: 144
No CNAME, and No A record found for this subdomain but still it came on the output of first shuffledns run.