Unable to complete SAML authentication

We have OBIEE 11g protected by OAM 11.1.2.2.

Our Customer is the Identity provider and OAM acting as a Service provider. After exchanging the metadata and setting up the IDP profile on our end and setting the Authentication Scheme for protected OBIEE resource to the IDP's generated authentication scheme, an IDP initiated request results in a customer login page, where the customer is able to login.

But the SAML sso action remains incomplete with OAM throwing the error "A System error has occured, please contact your system admin". OAM logs throw the following error.

We are unable to determine what configuration mistake causes this. Any help is appreciated.