RPAQ_GET_AF_0168 Inconsistent Results

I used this FM successfully in another program so when I needed it again I just copied what I had and used it:

CALL FUNCTION 'RPAQ_GET_AF_0168'
    EXPORTING
      c_it0168  = gv_pa0168
    IMPORTING
      af_values = gv_p0168_af
    TABLES
      af_fields = gt_rhtext_field.

However, even if I pass the exactly same PA0168 record in the new program the structure gv_p0168_af is "empty" (all initial values) whereas the other program, with the same 168 record, returns actual results.

I'm at a loss. Any ideas as to what might be going on?