Hi,
I got that error a few months ago and I was able to fix it by doing the following:
1. I disabled the modules: Domain controller and DNS and save changes.
2. I did a mark in the log files: /var/log/zentyal/zentyal.log and /var/log/syslog.
3. I enabled the DNS module and checked its status, including the mentioned log files.
4. Then, I enabled the domain controller module and again, I checked its status and the log files.
5. Finally, I tried to restart the DNS module just to see if the module still failed.
Hope it helps.
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