Pihole, Unbound and DNS - 1st attempt fails, 2nd time succeeds

Expected Behaviour:

For example:
If I hit Send in Thunderbird client to reply to email (pick any: Gmail, Hotmail, Yahoo, etc.), the immediate response is that the server cannot be contacted. If I hit Retry, the reply is sent.

This issue occurs with any operation that requires DNS.

  • Operating System (Family and Version) Debian GNU/Linux 12 (bookworm) aarch6
  • Hardware Raspberry Pi 3 Model B Plus Rev 1.3
  • Docker compose file or Docker run command n/a
  • Docker engine version n/a
  • Kernel 6.1.69-v8+
    Pihole & Unbound on this server
    All external DNS servers are unchecked in Pihole settings and custom DNS setting is:
    127.0.0.1#5353
    OPNsense is the router/firewall with Unbound not in service (never was)

Actual Behaviour:

1st attempt ALWAYS fails; 2nd attempt works. Doesn't matter which FQDN I use to illustrate my issue, the result is the same.

Please help me reconfigure my Pihole/Unbound settings:
Here is a representative example: (1s command fails, 2nd command, identical, succeeds)

$ dig 1.debian.pool.ntp.org
;; communications error to 127.0.0.1#53: timed out
;; communications error to 127.0.0.1#53: timed out
;; communications error to 127.0.0.1#53: timed out

; <<>> DiG 9.18.33-1~deb12u2-Debian <<>> 1.debian.pool.ntp.org
;; global options: +cmd
;; no servers could be reached
$ dig 1.debian.pool.ntp.org

; <<>> DiG 9.18.33-1~deb12u2-Debian <<>> 1.debian.pool.ntp.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28713
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;1.debian.pool.ntp.org.		IN	A

;; ANSWER SECTION:
1.debian.pool.ntp.org.	61	IN	A	23.186.168.129
1.debian.pool.ntp.org.	61	IN	A	50.188.3.205
1.debian.pool.ntp.org.	61	IN	A	198.137.202.56
1.debian.pool.ntp.org.	61	IN	A	23.186.168.125

;; Query time: 3 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Mon Apr 14 20:26:41 CDT 2025
;; MSG SIZE  rcvd: 114

$ 

Debug Token:

tail end:
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