HI Tarun,
What is your current version of Java(Portal)?
Are these users, who are facing issue with password change from portal, able to change the password while logging to ABAP system directly?
From the logs posted by you I understand that SSO is configured for this system , please confirm if my understanding is correct?
Please refer the below SAP note with details on similar error(not the same)
891614 - Login problems / Expired password
Also, please check if the initial password for these users has expired in the back-end system?
Regards,
Pradeep