We apply zabbix template to the server using the "Import" option available in UI. Say, template A is linked with another template B (A -> B) and the templates are applied to the zabbix server.
In the next version/release :
Now, if I try to import the latest version of the template (A -> C) on top of older version (A -> B) from the "import" option in UI, I get the following error :
Item "<Item_Key>" already exists on "<Template_Name>", inherited from another template.
But, as you can understand, in the latest version of the template (A -> C), template B is no longer there and hence there is no question of conflict between items in B and C.
Zabbix Version : 2.4.7
Update : Detailed steps to reproduce along with the sample templates are available here.
This looks like a bug in Zabbix and we thank you for reporting it at ZBX-10254.