I'm in the process of switching some servers to being monitored by a proxy (instead of the server itself). These servers already exist as hosts in Zabbix (through auto-registration).
When I switched the configuration for the hosts to be monitored by a proxy, they ended up getting a duplicate Zabbix Agent interface added to their profile. If my understanding is correct, this should not happen. The auto-registration process should only add a new interface if it does not already exist.