Can't add RFB as a reference in Contract.

Hello,

In contract BP Line Item we need to add reference of RFB awarded line item in each contract line item.

Steps that I did to do that:

1- Create Bidding BP Picker data element

2- Create Bidding BP line item Picker data element

3- Add new reference in Contract Reference Processes

4- Add created elements in this Reference

The problem is once I press OK and open reference again, Source Element of Line Item RFB BP disappeared, What is the solution of this issue?

Thanks,

Eslam