[keycloak-user] Invalid credentials for ldap

I have added a novell ldap user federation. When I try to login I get an error page displaying: Unexpected error when handling authentication request to identity provider. In the server log it shows a WARN message with "error=invalid_user_credentials" If I try to login with an incorrect user the message contains "error=user_not_found", so the user must have been found. It seems that some unexpectec error occurs while verifying the password. I'm sure it is correct. And I'm assuming that I would not get an unexpected error page if the password is just incorrect. Any help would be appreciated.