Failure connecting to Domain Controller to reset some Active Directory passwords.
Problem with network address configuration.
If you currently have your Domain Controller Managed System configured to point to your domain name, rather than one particular domain controller, this could potentially affect the success of your Scheduled Automatic Password Changes and could account for the fact that some succeed while others fail.
If your PPM is connecting to multiple domain controllers in a round-robin fashion, then network connection issues or connection timeouts when connecting to a particular domain controller will result in that particular password change failing.
A workaround for this issue is to specify the network address of a specific Domain Controller to connect to, to reset the passwords. This way PPM will always attempt to connect to that particular server and could help to resolve this issue.