Error while assigning the role to user using Rest API

I am using 'wso2am-2.5.0' and 'wso2is-km-5.6.0'. I am facing the below error while assigning the role to user using Rest SCIM API.

TID: [2] [] [2018-09-20 19:41:45,526] WSO2.ORG/test@abc.com@abc.com [2] [IS]ERROR {org.wso2.charon.core.protocol.endpoints.GroupResourceEndpoint} -  org.wso2.charon.core.exceptions.CharonException: Error occurred while updating old group : INTERNAL/privileged

Steps:

1. Created the Internal Group/Role through SCIM Rest API . Example : INTERNAL/<RoleName>

2. Created user through SCIM Rest API for the secondary User store (JDBC Based) Example : SECUSERSTORE/<username>

3. Now trying to assign the INTERNAL/<RoleName> to SECUSERSTORE/<username> using SCIM Rest APIs

This assignment of role is successful when I try it through the management console.

It is failing when I try to do the same using the Rest APIs.