docker.finaltek.net has no CNAME records.
Question and response
Question
dig docker.finaltek.net. NS
Answer
The response has no answer records.
Authority
finaltek.net. 1719 SOA ns.gransy.com. root.gransy.com. 2771766257 86400 900 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0