Failed DNS update - with error code 110

[maxulm]

Good morning everyone,

last year I've configured my TS-253be to work as a domain controller.
Everything works fine, but every ten minutes the following entry appears in the log.samba:
[2020/04/21 09:32:34.469165, 0] ../source4/dsdb/dns/dns_update.c:290(dnsupdate_nameupdate_done)
../source4/dsdb/dns/dns_update.c:290: Failed DNS update - with error code 110

After searching on the internet, I've reconfigured the dns forwarder entry in the smb.conf from 127.0.1.1 to the IP-Address of my router, but it hasn't solved my problem.
After a few hours samba's crashing because of these errors, so I have to restart it.
As a workaround I've created a cron job to do this every 4 hours, but I don't like this "solution".
Not at least because of the fact that the DNS Server in the domain becomes offline every 4 hours.
Is there anyone could help me?

Thx!