The user's password is set with
pem.setMemberPassword POA API method. The user is able to login to his customer's control panel (CCP) with this password, but on attempt to change it from Parallels Panel > Account > Change Password > user an error occurs:
Your own password is wrong.
How is that possible for the user that could login to CCP with the password set?
The customer logs in using POA password. The screen for changing the password is generated by PBA and the password is validated against the user's password in PBA. The POA API method
pem.setMemberPassword sets the user's password in POA only, it does not change the password on PBA side. So, the cause of the error is different user's passwords in PBA and POA.
Password for the affected user can be changed from the provider's control panel (as verification of the current password is not required there).