Thanks for your post!
Case #MODULE-7059 is open with our development team to ensure that the DirectAdmin module is accurately returning success/failure when module actions are performed. At present, success is being returned in some cases, where the action being performed was not successful.
In respect of changing passwords through the DirectAdmin module, this is functionality that does presently work, however, if any errors are encountered on the server when changing a services password (the most common one being the servers credentials set within WHMCS being wrong, so the change password action fails), due to case #MODULE-7059, this will may be shown in WHMCS as successful, when it was not.
In summary, #MODULE-7059 is open to ensure that the DirectAdmin module is correctly displaying success or failure for module actions, not to correct an issue with changing service passwords, which is a feature that presently works. If changing services passwords is not working for you, please respond to us in the ticket where we highlighted this case to you, so we can work with you to determine what issue/error/configuration is preventing you from changing service passwords within WHMCS.