Function Module BINARY_RELATION_CREATE exception internal_error

Hi guys,

sometime I get expetion internal_error from FM BINARY_RELATION_CREATE while trying to create the binary relationship to the Order (Order = e.g. AUFK-AUFNR). Please help me to find out, why sometimes I get some error and sometimes it works fine.

CALL FUNCTION'BINARY_RELATION_CREATE'
     EXPORTING
       obj_rolea            = is_object
       obj_roleb            = is_attachment
       relationtype         = 'ATTA'
    IMPORTING
      binrel               = binrel
    TABLES
      binrel_attrib        = binrel_attrib
    EXCEPTIONS
      no_model             = 1
      internal_error       = 2
      unknown              = 3
      OTHERS               = 4
     

Thanks and regards

Britta