nslookup slow and can't resolve any pool.ntp.org names

[MarkA]

Hi Folks, During my last update (to 384.6) yesterday I noticed in the logs that NTP didn't appear to be updating (continuous 'ntp: start NTP update entries') for a NTP server setting of pool.ntp.org (and the time was months off).

From a local ssh login to the router when I run an nslookup for pool.ntp.org, the response takes almost 40 seconds and returns with:

admin@RT-AC56U-5848:/# nslookup pool.ntp.org
Server:    127.0.0.1
Address 1: 127.0.0.1 localhost.localdomain

nslookup: can't resolve 'pool.ntp.org'

If I specify an external DNS server I get an immediate successful response:

admin@RT-AC56U-5848:/# nslookup pool.ntp.org 9.9.9.9
Server:    9.9.9.9
Address 1: 9.9.9.9 dns.quad9.net

Name:      pool.ntp.org
Address 1: 64.113.44.55 ip7.nsg.sbbsnet.net
Address 2: 172.98.77.203 mta5.1strepublicwebsites.com
Address 3: 64.6.144.6 triangle.kansas.net
Address 4: 72.5.72.15 mirror1.sjc02.svwh.net

Local resolution for other names does work but is slow. google.com resolution takes about 20 seconds and comes back as so:

admin@RT-AC56U-5848:/# nslookup google.com
Server:    127.0.0.1
Address 1: 127.0.0.1 localhost.localdomain

Name:      google.com
Address 1: 2607:f8b0:4002:c0c::64
Address 2: 74.125.138.101 yi-in-f101.1e100.net
Address 3: 74.125.138.102 yi-in-f102.1e100.net
Address 4: 74.125.138.113 yi-in-f113.1e100.net
Address 5: 74.125.138.100 yi-in-f100.1e100.net
Address 6: 74.125.138.139 yi-in-f139.1e100.net
Address 7: 74.125.138.138 yi-in-f138.1e100.net

Using external DNS is immediate, but different result:

admin@RT-AC56U-5848:/# nslookup google.com 9.9.9.9
Server:    9.9.9.9
Address 1: 9.9.9.9 dns.quad9.net

Name:      google.com
Address 1: 2607:f8b0:4007:80b::200e lax02s23-in-x0e.1e100.net
Address 2: 216.58.194.174 sfo07s13-in-f14.1e100.net

I am currently using an IP address of one of the ntp pool servers for the ntp settings, which works, but something is not right here when trying to use DNS for the NTP servers. Also the tools pages in the router GUI all fail to resolve the ntp server names as well for ping, nslookup, etc. I tried several of the ntp.org prefix names too (north-america.pool.ntp.org, etc.) with the same results. Client computers connecting to the router and using router DNS setting (9.9.9.9) all resolve these fine.

My Configuration:
RT-AC56U, 384.6_0
DHCP Enabled
Domain Name: not-specified/blank
Default Gateway: not-specified/blank
DNS Server 1: 9.9.9.9
DNS Server 2: 149.112.112.112
Router IP: 192.168.1.1
Operation Mode: Wireless router

Thanks