ubuntu – (BIND9) Domains within a certain area stop resolving randomly / intermittently

I've been stuck for a while with an error related to bind9 and particular domains within a zone. Sometimes, the resolution of one or more random domains within the zone ("error zone", let's say) stops working, affecting one day example1.errorzona and another day example4.errorzona, ejemplo5.errorzona, etc. The rest of my zones work perfectly every hour.

The records say: called[20450]: client 192.168.50.20 # 64165 (example3.errorzone): query (cache) & # 39; example3.errorzone / A / IN & # 39; denied

The solution at this time is to restart the Bind9 service, but I can no longer afford it. I could not find the problem nor the original cause.

Current options of named.conf.options (edited networks, etc.):

acl myLAN {
172.20.0.0/16;
192.168.50.0/24;
};

options {
"/ etc / bind /" directory;
forwarders {
8.8.8.8;
dnsISP1;
dnsISP2;
10.20.30.40;
};

allow-query {
myLAN;
};

permission-recursion {
myLAN;
};  

}; *

Errorzone named.conf:

zone "error zone" {
write forward
promoters {10.20.30.40;};
};  

Bind9 version: 9.9.5-3ubuntu0.18-Ubuntu

Could someone give me a hand? I ran out of ideas
Thanks, any information will be greatly appreciated.