this last information does not help.
what would help would be to answer to those question
1 have you delegated the dns work to an external provider ?
2 a dig (using a brand new ip to test) would be more helpful directly on the server with the dnscache log and dnscache.forwarder log
why dig? because you will get the query time
1 Have not changed dns servers
[root@post ~]# dig 16.225.49.37.zen.spamhause.org any
; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.5 <<>> 16.225.49.37.zen.spamhause.org any
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1549
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;16.225.49.37.zen.spamhause.org. IN ANY
;; ANSWER SECTION:
16.225.49.37.zen.spamhause.org. 600 IN A 95.211.219.67
;; Query time: 144 msec
;; SERVER: 10.0.1.253#53(10.0.1.253)
;; WHEN: Sat Jul 31 21:15:30 BST 2021
;; MSG SIZE rcvd: 64
AND
2021-07-31 21:15:30.601370500 query 3166 7f000001:87fc:ff07 255 16.225.49.37.zen.spamhause.org.
2021-07-31 21:15:30.601426500 cached ns org. d0.org.afilias-nst.org.
2021-07-31 21:15:30.601428500 cached ns org. a0.org.afilias-nst.info.
2021-07-31 21:15:30.601429500 cached ns org. c0.org.afilias-nst.info.
2021-07-31 21:15:30.601429500 cached ns org. a2.org.afilias-nst.info.
2021-07-31 21:15:30.601430500 cached ns org. b0.org.afilias-nst.org.
2021-07-31 21:15:30.601431500 cached ns org. b2.org.afilias-nst.org.
2021-07-31 21:15:30.601462500 cached 1 d0.org.afilias-nst.org.
2021-07-31 21:15:30.601464500 cached 1 a0.org.afilias-nst.info.
2021-07-31 21:15:30.601464500 cached 1 c0.org.afilias-nst.info.
2021-07-31 21:15:30.601493500 cached 1 a2.org.afilias-nst.info.
2021-07-31 21:15:30.601494500 cached 1 b0.org.afilias-nst.org.
2021-07-31 21:15:30.601495500 cached 1 b2.org.afilias-nst.org.
2021-07-31 21:15:30.601524500 tx 0 255 16.225.49.37.zen.spamhause.org. org. c7f97001 c7f97801 c7133801 c7133901 c7133501 c7133601
2021-07-31 21:15:30.609988500 rr c7f97001 86400 ns spamhause.org. ns1.hastydns.com.
2021-07-31 21:15:30.609990500 rr c7f97001 86400 ns spamhause.org. ns2.hastydns.com.
2021-07-31 21:15:30.610044500 stats 3166 709818 40 0
2021-07-31 21:15:30.610045500 cached ns com. a.gtld-servers.net.
2021-07-31 21:15:30.610045500 cached ns com. l.gtld-servers.net.
2021-07-31 21:15:30.610046500 cached ns com. e.gtld-servers.net.
2021-07-31 21:15:30.610047500 cached ns com. b.gtld-servers.net.
2021-07-31 21:15:30.610048500 cached ns com. i.gtld-servers.net.
2021-07-31 21:15:30.610078500 cached ns com. d.gtld-servers.net.
2021-07-31 21:15:30.610079500 cached ns com. g.gtld-servers.net.
2021-07-31 21:15:30.610080500 cached ns com. f.gtld-servers.net.
2021-07-31 21:15:30.610081500 cached ns com. h.gtld-servers.net.
2021-07-31 21:15:30.610112500 cached ns com. c.gtld-servers.net.
2021-07-31 21:15:30.610113500 cached ns com. j.gtld-servers.net.
2021-07-31 21:15:30.610113500 cached ns com. k.gtld-servers.net.
2021-07-31 21:15:30.610114500 cached ns com. m.gtld-servers.net.
2021-07-31 21:15:30.610144500 cached 1 a.gtld-servers.net.
2021-07-31 21:15:30.610145500 cached 1 l.gtld-servers.net.
2021-07-31 21:15:30.610146500 cached 1 e.gtld-servers.net.
2021-07-31 21:15:30.610175500 cached 1 b.gtld-servers.net.
2021-07-31 21:15:30.610176500 cached 1 i.gtld-servers.net.
2021-07-31 21:15:30.610177500 cached 1 d.gtld-servers.net.
2021-07-31 21:15:30.610206500 cached 1 g.gtld-servers.net.
2021-07-31 21:15:30.610207500 cached 1 f.gtld-servers.net.
2021-07-31 21:15:30.610237500 cached 1 h.gtld-servers.net.
2021-07-31 21:15:30.610238500 cached 1 c.gtld-servers.net.
2021-07-31 21:15:30.610239500 cached 1 j.gtld-servers.net.
2021-07-31 21:15:30.610266500 cached 1 k.gtld-servers.net.
2021-07-31 21:15:30.610267500 cached 1 m.gtld-servers.net.
2021-07-31 21:15:30.610297500 tx 0 1 ns1.hastydns.com. com. c029a21e c01f501e c00c5e1e c0304f1e c02bac1e c02a5d1e c005061e c01a5c1e c023331e c034b21e c036701e c0210e1e c037531e
2021-07-31 21:15:30.625890500 rr c029a21e 172800 1 ns1.registermatrix.com. d420f031
2021-07-31 21:15:30.625935500 rr c029a21e 172800 1 ns2.registermatrix.com. cff4443e
2021-07-31 21:15:30.625936500 rr c029a21e 172800 ns hastydns.com. ns1.registermatrix.com.
2021-07-31 21:15:30.625937500 rr c029a21e 172800 ns hastydns.com. ns2.registermatrix.com.
2021-07-31 21:15:30.625938500 stats 3166 710002 40 0
2021-07-31 21:15:30.625966500 cached 1 ns1.registermatrix.com.
2021-07-31 21:15:30.625967500 cached 1 ns2.registermatrix.com.
2021-07-31 21:15:30.625968500 tx 0 1 ns1.hastydns.com. hastydns.com. cff4443e d420f031
2021-07-31 21:15:30.710083500 rr cff4443e 300 1 ns1.hastydns.com. 45a25032
2021-07-31 21:15:30.710138500 stats 3166 710046 40 0
2021-07-31 21:15:30.710139500 cached ns hastydns.com. ns1.registermatrix.com.
2021-07-31 21:15:30.710141500 cached ns hastydns.com. ns2.registermatrix.com.
2021-07-31 21:15:30.710142500 cached 1 ns1.registermatrix.com.
2021-07-31 21:15:30.710143500 cached 1 ns2.registermatrix.com.
2021-07-31 21:15:30.710173500 tx 0 1 ns2.hastydns.com. hastydns.com. d420f031 cff4443e
2021-07-31 21:15:30.725369500 rr d420f031 300 1 ns2.hastydns.com. 5fd375ce
2021-07-31 21:15:30.725412500 stats 3166 710090 40 0
2021-07-31 21:15:30.725413500 tx 0 255 16.225.49.37.zen.spamhause.org. spamhause.org. 5fd375ce 45a25032
2021-07-31 21:15:30.744398500 rr 5fd375ce 600 1 16.225.49.37.zen.spamhause.org. 5fd3db43