Dump UNICODE_TYPES_NOT_CONVERTIBLE. Warum?

Code: Alles auswählen.

  move 'TABNAME' to gv_qtabname.
  CALL FUNCTION 'DDIF_NAMETAB_GET'
    EXPORTING
      TABNAME   = gv_qtabname
    TABLES
      DFIES_TAB = gt_itab
    EXCEPTIONS
      NOT_FOUND = 1
      OTHERS    = 2.

<...>

  loop at gt_itab .
    move: gt_itab-fieldname to ls_alv_cat-fieldname
        , gv_qtabname       to ls_alv_cat-ref_table
        , gt_itab-fieldname to ls_alv_cat-ref_field
        , c_x               to ls_alv_cat-lowercase
        .
    append ls_alv_cat to lt_alv_cat.
  endloop.

  CALL METHOD cl_alv_table_create=>create_dynamic_table
    EXPORTING
      it_fieldcatalog = lt_alv_cat
    IMPORTING
      ep_table        = lv_qdref.

  assign: lv_qdref->* to <fs_qtable>.
  create data lv_qzeile like line of <fs_qtable>.
  assign lv_qzeile->* to <fs_qwa>.

<...>

  select * from  (gv_qtabname)
           into  corresponding fields of table <fs_qtable>
           for   all entries in ...
           where ...

<...> Jetzt werden die daten von <fs_qtable> bearbeitet <...>

      loop at <fs_qtable> into <fs_qwa>.
        if <fs_status> eq irgendeinebedingung.
          insert (gv_qtabname) from <fs_qwa>.  <== HIER ERFOLGT DER DUMP
        endif.
      endloop.