DNS load balancing issue

[Satay Epic]

Hello,

I've NGINX 1.12-1 running on CentOS 7.2 and being used for DNS load
balancing. However I'm seeing lots of errors in the "dns.log".. I've
no access to the system right now but error was like.. "No response
received from the upstream server" The occurrence of the errors is no
continuous but it's pretty frequent.

The three backend servers are  Windows 2012 R2 DNS servers

I will provide the nginx.conf details soon.

I may have to do some tuning besides upgrade to an appropriate version
I guess.  Can anyone help to suggest/recommend tuning to minimize the
errors or rather not to have them at all?

Thanks