Error while initial sync of Users from SAP system using SAP Connector in One IM 8.1

I am getting below error while iperforming initial sync of users from SAP system.

Error loading system object for class USER(all) USER_Master.
System.NulReferenceException: Object reference not set to an instance of an object

I am able to import rest of the data from SAP system like role,profile,groups,etc. and facing issue only while reconciliation of USERS

KIndly suggest the workaround to fix this issue.

Thanks