DNS error on one of the subdomains. Where to dig?

Question

Domain Name System

The DNS domain is located on Yandex. Subdomains are organized using apache directives (there is also nginx, but it does not resolve subdomains, everything is fine there) :

<VirtualHost 127.0.0.1:8080>
        ServerName   www.domain.ru
        ServerAlias  *.domain.ru
        ServerSignature Off
        RewriteEngine on
        ...
        DocumentRoot /.../domain.ru/www
        VirtualDocumentRoot /.../domain.ru/%1

As a result, since recently, one (only one) of the subdomains is periodically unavailable with a response like:
Unable to determine the IP address from the host name
The DNS server replied: No DNS records
ERR_NAME_NOT_RESOLVED
The rest are working normally. All subdomains on the same engine.
Guru, tell me where to dig? In code, .htaccess, etc. I don't see any reason.
PS "I didn't touch anything, it's on its own..."
UPD: As a crutch , I explicitly registered a subdomain in Yandex.Connect (all the rest are sorted through *). Is not a fact. because of this, but it worked. An inquisitive mind does not leave hope to deal with what happened and bring DNS records to their original (correct) state.

Answer 1

service name possible