Thanks for the reply. DeepFreeze almost acts as a snapshot. It will back out any changes that are made to the computer to it's original frozen state after reboot. That is what I suspect is happening, the computer object is changing its password after the default 30 days, and if the computer is rebooted it reverts to the old password hash and the passwords are no longer synched between the Mac and AD.
I'm not sure if disabling password changes with Group Policy will work with Express. This article explains the setting: https://technet.microsoft.com/en-us/library/jj852191.aspx
Is it possible to disable the password changes on the Mac with Centrify Express?