dns186.b.register.com has no CNAME records.
Question and response
Question
dig dns186.b.register.com. NS
Answer
The response has no answer records.
Authority
register.com. 1659 SOA heidi.ns.cloudflare.com. dns.cloudflare.com. 2397330442 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0