Expert routine (look up) issue

Hello BI experts,

In a transformation from a DSO 1 to another DSO 2, I have written an expert routine and applied a look up on another DSO 3 to bring some date fields.

When I load the data applying a selection criteria on one record in DTP, the look up works and date field is populated in DSO 2.

However, when I remove the selection criteria in DTP and load the data (full load DTP) the look up does not works and the date fields are blank.

Has anyone faced this issue before? 

Thanks,

Vasanti