Dns Errors Very Often

there is "Cannot Resolve Dns" for my site for one or 2 regions .. Everytime i check my site my site with a Website Monitoring site , i get Cannot Resolve Dns for one or two regions .. can anyone please tell me what the problem can be ..

When i go to dnsreport.com , i get Fail in Missing (stealth) nameservers

Quote:

FAIL: You have one or more missing (stealth) nameservers. The following nameserver(s) are listed (at your nameservers) as nameservers for your domain, but are not listed at the parent nameservers (therefore, they may or may not get used, depending on whether your DNS servers return them in the authority section for other requests, per RFC2181 5.4.1). You need to make sure that these stealth nameservers are working; if they are not responding, you may have serious problems! The DNS Report will not query these servers, so you need to be very careful that they are working properly.

ns1.mysite.ws.
ns2.mysite.ws.
This is listed as an ERROR because there are some cases where nasty problems can occur (if the TTLs vary from the NS records at the root servers and the NS records point to your own domain, for example).