Urgent: Since installing the last major update my DNS has stopped working

[HankM]

I've got 3 x DNS servers. The Master server has 4 forwarders. One to the AD server, one to my ISP's DNS, one to Google and one to Dynu.

It's all worked fine until the big update, now the DNS forwarders are 'unavailable' (but I can ping them from the server).

dig acme-v02.api.letsencrypt.org

; <<>> DiG 9.11.36-RedHat-9.11.36-11.el8_9.1 <<>> acme-
v02.api.letsencrypt.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 16823
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 521eb6b59732065e (echoed)
;; QUESTION SECTION:
;acme-v02.api.letsencrypt.org.   IN   A

;; Query time: 1 msec
;; SERVER: 192.168.0.240#53(192.168.0.240)
;; WHEN: Tue May 14 17:05:49 CEST 2024
;; MSG SIZE  rcvd: 69

Something to do with DNS must have changed since I first setup OPNS a long time ago and I never set anything other than aliases and rules. Never touched the DNS or anything else, it's a really simple system, just block the criminals.

Can anyone help please, it's become a major issue