Steps to reproduce:

1. Create host group "test"
2. Create new host "test host", add to group "test"
3. Create new template "test template", add to group "test"
4. Create new item on "test template" called "test item", item key "test"
5. Navigate to items screen for "test template", check the "test item" checkbox, click the "copy" button
6. Select the "Hosts" radio box.
7. In "Target" type "test" and click the "test host" host.
8. Click "Copy"

Result:

Expected:
Unknown