Hi Venkat,
Error XR028 usually occurs when you have data inconsistency between CRM and ERP.
For example,
If there is a BP 111 have a contact person 222 in CRM.
But the ERP customer 111 doesn't have any contact person.
When you delete the relationship in CRM system, error XR028 occurs.
So please check if you have any contact person data inconsistency.
And please check whether note 703322 helps.
Best Regards & Thanks
Dean Yan