*.pool.ntp.dockersrc.us has no AAAA records.
Question and response
Question
dig casjay.pool.ntp.org. AAAA
Answer
The response has no answer records.
Authority
pool.ntp.org. 1300 SOA i.ntpns.org. hostmaster.pool.ntp.org. 1772677264 5400 5400 1209600 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0