'Ticket Manage: View Ticket' Save button missing

Hello,

When I access a detail of a ticket from the back-end,
I can't find any Save (or Submit) button in it,
even though I logged-in as super user.



Is this a bug?

When I click the [Change Ticket Category] button, I noticed that the Category is changed and saved.
For Ticket Status and Priority, these buttons also work good.

But clicking the [Apply Label] button doesn't apply label (the save action doesn't occur).
Let me see how to solve.
Thank you in advance.