Why doesn't Windows 7 use a secondary DNS server?

Question

Domain Name System

Faced a strange thing.
There are two DCs in the domain, on both, as usual, on the DNS server. Users in the properties of the network, respectively, have two DNS servers, primary and secondary.
But when the main one falls off, Windows 7 PCs still access it and therefore cannot resolve the names. The second normally nslukapit manually.
Question: bug or feature? MB crooked hands of admins, who set everything up?
UPD. Debian did a great job with switching to secondary, by the way, but for some reason Windows 7 didn't. Regarding the responses from the primary DNS server (not the network interface) - it seems they were not there.

Answer 1

Only when the DNS client gets to (2) will other servers be queried.
Full article

Answer 2

It is very likely that you either have a virus or some kind of tool preventing you from changing DNS.
If I am not confusing anything, then the server change occurs if more than 30% of the packets were returned with an error (or not returned).