Comment 15 for bug 1787739

Same results using the vagrant vm configured bind server:

vagrant@ubuntu-bionic:~$ nslookup ubuntu.com - 192.168.0.130
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: ubuntu.com
Address: 91.189.94.40
** server can't find ubuntu.com: SERVFAIL

vagrant@ubuntu-bionic:~$ nslookup amazon.com - 192.168.0.130
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: amazon.com
Address: 176.32.103.205
Name: amazon.com
Address: 205.251.242.103
Name: amazon.com
Address: 176.32.98.166
** server can't find amazon.com: SERVFAIL

vagrant@ubuntu-bionic:~$ nslookup google.com - 192.168.0.130
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: google.com
Address: 172.217.3.14
Name: google.com
Address: 2607:f8b0:400f:801::200e

vagrant@ubuntu-bionic:~$

Pauses are the same upon the first nslookup for the domain. After the first lookup, the entry is cached and there isn't a pause between the ipv4 and ipv6 entries.

You can see the pause in the strace output (attached):
vagrant@ubuntu-bionic:~$ strace -ftt nslookup cononical.com - 192.168.0.130 2> strace.out

[pid 1836] 18:39:56.769691 futex(0x7f5ae18c30c8, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid 1838] 18:39:57.576985 <... epoll_wait resumed> [{EPOLLIN, {u32=20, u64=20}}], 64, -1) = 1

Also doing some playing with nslookup and IPV6 settings:

vagrant@ubuntu-bionic:~$ nslookup
> server 192.168.0.130
Default server: 192.168.0.130
Address: 192.168.0.130#53
> ubuntu.com
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: ubuntu.com
Address: 91.189.94.40
** server can't find ubuntu.com: SERVFAIL
> set querytype=a
> ubuntu.com
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: ubuntu.com
Address: 91.189.94.40
> set querytype=aaaa
> ubuntu.com
Server: 192.168.0.130
Address: 192.168.0.130#53

** server can't find ubuntu.com: SERVFAIL
> google.com
Server: 192.168.0.130
Address: 192.168.0.130#53

Non-authoritative answer:
Name: google.com
Address: 2607:f8b0:400f:800::200e

So definitely something going on with the IPV6. In your configuration, do you get IPV6 records for google.com?