Steps to reproduce:

1. Create (parent) template with an item, e.g. HTTP agent, with update interval e.g. 5m and "do not keep history" set.
2. Create other template and link parent template (make it child).
3. Assign child template to host.
4. Try to change update interval e.g. to 1m and storage period e.g. 90d on child template level and also on host level.

Result:
In both cases, output is green, "Item updated" without any error, but after reopening that inherited item, nothing is changed.
Expected:
Change of inherited item to be persistent, when UI allows to change that fields.