Consider the following situation...
This is expected behavior. In the above situation, the user's "lockoutTime" attribute is not reset to a value of 0. Change Auditor is designed to only produce an event when the value changes to 0 (user account unlocked) or from 0 (user account locked).
The two ways to have this value change to 0 after being locked out is to either have an administrator unlock the account via Active Directory Users and Computers, or by the user successfully logging in with the proper credentials after the automatic unlock period.