# dig +trace SERVER-BUSINESS.RU
...
SERVER-BUSINESS.ru. 345600 IN NS oxygen.ns.hetzner.com.
SERVER-BUSINESS.ru. 345600 IN NS hydrogen.ns.hetzner.com.
SERVER-BUSINESS.ru. 345600 IN NS helium.ns.hetzner.de.
;; Received 644 bytes from 194.190.124.17#53(d.dns.ripn.net) in 72 ms
...
SERVER-BUSINESS.RU. 3600 IN A 135.181.20.85
SERVER-BUSINESS.RU. 3600 IN NS robotns3.second-ns.com.
SERVER-BUSINESS.RU. 3600 IN NS robotns2.second-ns.de.
SERVER-BUSINESS.RU. 3600 IN NS oxygen.ns.hetzner.com.
SERVER-BUSINESS.RU. 3600 IN NS ns2.SERVER-BUSINESS.RU.
SERVER-BUSINESS.RU. 3600 IN NS helium.ns.hetzner.de.
SERVER-BUSINESS.RU. 3600 IN NS hydrogen.ns.hetzner.com.
SERVER-BUSINESS.RU. 3600 IN NS ns1.first-ns.de.
SERVER-BUSINESS.RU. 3600 IN NS ns1.SERVER-BUSINESS.RU.
;; Received 316 bytes from 193.47.99.5#53(helium.ns.hetzner.de) in 77 ms
То есть, на родительском NS-сервере указаны только три NS-сервера, а на основном NS-сервере их указано восемь. А эти списки должны совпадать.
