UNION syntax different for 7.1.2

Hello,

    from 7.0.2 to 7.0.3, the following script works fine, but in 7.1.2 I must remove the rr. from ORDER BY clause. This
happensonly when I have a UNION between the selects, if I try the order by rr.dtsolicitacao in both selects everything
goesok. I know you guys can suggest me to change this whole script to a single outer join, but I cant because my app
stillaccess some old 7.0.3 databases spread over all my country. The question is : Is it some kind of bug or I need to
changeall my scripts that uses UNION ? 

Best regards,

José Vilson de Mello de Farias
Dígitro Tecnologia Ltda - Brazil

SELECT
  rr.*, rm.identificacao, rr.tipo_arquivo,
  ru.cod_operador, ru.cod_operador as nome,
  ru.flg_responsavel, ri.flg_estado as flg_estimp,
  ri.msg_erro as msg_erroimp
FROM
  rel__relatorio rr, rel__modelo rm,
  rel__usuarios ru, rel__impressao ri
WHERE
  rr.cod_cad_relatorio = 1 AND
  rr.cod_modelo = rm.cod_modelo  AND
  rr.cod_cad_relatorio = ru.cod_cad_relatorio AND
  rr.cod_relatorio = ru.cod_relatorio AND
  ru.cod_cad_relatorio = ri.cod_cad_relatorio AND
  ru.cod_relatorio = ri.cod_relatorio AND
  ru.cod_operador = ri.cod_operador AND
  rr.cod_terminal = 'dgtac' AND
  ri.dtimpressao IS NULL AND    ru.cod_operador = 'SYSADM'
UNION ALL
SELECT
  rr.*, rm.identificacao, rr.tipo_arquivo,
  ru.cod_operador, ru.cod_operador AS nome,
  ru.flg_responsavel, NULL, NULL
FROM
  rel__relatorio rr, rel__modelo rm,
  rel__usuarios ru
WHERE
  rr.cod_cad_relatorio = 1 AND
  rr.cod_modelo = rm.cod_modelo  AND
  rr.cod_cad_relatorio = ru.cod_cad_relatorio AND
  rr.cod_relatorio = ru.cod_relatorio AND    ru.cod_operador = 'SYSADM'  AND
  rr.cod_terminal = 'dgtac' AND
  NOT EXISTS (SELECT * FROM rel__impressao ri WHERE
    ru.cod_cad_relatorio = ri.cod_cad_relatorio AND
    ru.cod_relatorio = ri.cod_relatorio AND
    ru.cod_operador = ri.cod_operador) AND    ru.cod_operador = 'SYSADM'

ORDER BY rr.dtsolicitacao