We have some host that we use to monitor web sites. They had no items that use host interface - only HTTP, Dependent, Calculated, External and Internal - all of them from templates. Hosts was created a while ago when you have to add at least one interface, there was no option to create host without interface even if it actually don't need.

Now when i try to remove host interface, previously select "None" in every item (HTTP, External) that has it option in web interface, button "remove" is inactive (See host_parameters screenshot). Then we tried to export host, remove host interface and import it again and get error (See import_error screenshot) than interface is linked to an item, which type is "Dependent" and it has no option to choose host interface (See item_configuration screenshot). When we press "Update" button in request payload we can see selectedInterfaceId is not "0" (See request_payload screenshot). That behavior for host than monitor by server.

For proxy monitored web sites hosts behavior is different. We can remove host interface without any problem, but we broke proxy configuration (See zabbix_proxy.log)

Steps to reproduce (for proxy):

1. Remove host interface in host configuration in frontend;
2. Update proxy configuration;
3. Check zabbix_proxy.log for proxy configuration error.

Result:
See log file zabbix_proxy.log
Expected:
No problems with removing unused host interface.

Also noticed a mistake in error log message: cannot process proxy onfiguration data received from server - letter "c" is missing in word "configuration".