When defining the variable ZBX_SERVER_HOST, which is responsible for setting the Server= parameter in the Zabbix agent configuration file, the values assigned to this variable are also automatically applied to the ServerActive= parameter. This behavior generates errors when the agent attempts to communicate with those IPs. I believe the ideal configuration should be that the IPs assigned to the ZBX_SERVER_HOST variable are not automatically propagated to ServerActive=. Instead, the ZBX_ACTIVESERVERS variable should be explicitly configured for active checks.