As a Windows domain administrator, unlocking locked user account is part of the routine work. Besides user continually type in the wrong passwords, the below three senarios also can lead to the issue.
First, some users tend to keep their password remembered in applications like Internet browser. As this saves their time to type password each time. Unfortunately, not every user remember to update the rememberd password after they changed their AD password.
Second, some developers would like to use their own AD accounts in their code. For example, the product they are developing uses AD for authenticateion. The developers may embed their own credentiala into the code to verify whether the authentication works. If they unluckily forget to remove it and changed their AD password afterwards. They will get locked everytime when the code runs.
Third, users changed their AD password while a previously connected remote desktop session is still active.