vCenter vCSA DNS ip change related issue

we have one very strange issue which is causing because of changing our old DNS server IPs

I have changed old DNS ips to new DNS ips using local administrator account --- no issues found

logged-off from vcenter and trying to log-in back to vcenter using AD account --- we are having error message saying that invalid credentials

To me it looks AD integration in broken

This is totally unexpected behavior why would AD breaks with changing DNS IP address

vCSA version: 6.7 U2

can some one help me here?

Regards,
Volga