Problem with Workflow while using create record

Hi ,

I have created a custom entity Unit and Property . I am using a workflow to create records on this Property entity, when the unit status is sold in Unit entity. When I create the records I want to transfer some fields from Unit to Property. Everything works fine using Dynamic Fields to reference the fields I need from Unit, except when the field is an Lookup. In this case, the Dynamics field assistant doesn't show any fields..How can I solve this ?

Thanks,