Okay, looking at your error, It could be coming from an Server API
error. Please share the output from the following commands (please make
sure to not share any sensitive information like public addresses or
credentials):
$ journalctl -xeu wazuh-dashboard
$ grep -iE 'warning|error|critical' /var/ossec/logs/ossec.log
$ grep -iE 'warning|error|critical' /var/ossec/logs/api.log
Another detail we need is the Wazuh version you're using in your environment and the content of the rule file you're trying to save with your Dashboard editor, thus we can try and reproduce your error for further debugging.