bb.miniserver.cz has no CNAME records.
Question and response
Question
dig bb.miniserver.cz. NS
Answer
The response has no answer records.
Authority
miniserver.cz. 10800 SOA shinzon.blueboard.cz. hostmaster.shinzon.blueboard.cz. 2023023303 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0