Vanity nameserver with secondary dns hosting

I have set up a .pro domain with secondary DNS at buddyns.

Glue records at registrar:
ns1.box.domain.pro → IP of MIAB
ns2.box.domain.pro → IP of MIAB
ns3.box.domain.pro → IP of buddyns nameserver
ns4.box.domain.pro → IP of buddyns nameserver
ns5.box.domain.pro → IP of buddyns nameserver

The only error with the buddyns “delegration lab” testing tool

The list of nameservers declared by the last delegating server and the authoritative server do not match. This occasionally entails important issues. Configuration should be reviewed ASAP.

The rest of the info returned that looks fine (to me) is:

Master
ns1.box.domain.pro.

Administrator
hostmaster@box.domain.pro

Version serial
2019020812
Slave refresh
7200
Slave retry
1800
Slave expiry
1209600
Negative cache
1800

BuddyNS inquired server b2.pro.afilias-nst.org , which delegates zone domain.pro to:

  • ns1.box.domain.pro
  • ns2.box.domain.pro
  • ns3.box.domain.pro
  • ns4.box.domain.pro
  • ns5.box.domain.pro

*ns2.box. ns2.box.domain.pro is authoritative for zone domain.pro ! It provides this authority list:

  • ns1.box.domain.pro
  • ns3.box.domain.pro
  • ns4.box.domain.pro
  • ns5.box.domain.pro