nsb1.srv53.org has no CNAME records.
Question and response
Question
dig nsb1.srv53.org. NS
Answer
The response has no answer records.
Authority
srv53.org. 197 SOA ns1.srv53.org. support.dnshosting.org. 1590167505 1800 600 2419200 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0