Isn't attached the correct report

I made a email template for sale orders with the report attached. When I send for example the SO0015 sale I received the report
of SO001 sale, if i send the email again I receive the report of sale SO002.

Finally I fix the bug modifing the code of poweremail_send_wizard.py

I modified the function save_to_mailbox because I think that the id that is passed to generate the report was the id of email that has been sent. So I modified the code for generate the report with the id of the document that calls the wizard to send the email. I also modified the line that puts the name of the report and the name of the attached file. The code from the if self.template.report_template is:

if self.template.report_template:
                report_id = screen_vals['rel_model_ref'] #The correct report id
                reportname = 'report.' + self.pool.get('ir.actions.report.xml').read(cr,uid,self.template.report_template.id,['report_name'])['report_name']
                service = netsvc.LocalService(reportname)
                (result, format) = service.create(cr, uid, [report_id], {}, {})
                att_obj = self.pool.get('ir.attachment')
                new_att_vals={
                                'name':screen_vals['report'] + ' (Email Attachment)',
                                'datas':base64.b64encode(result),
                                'datas_fname':unicode(screen_vals['report'] or 'Report') + "." + format,
                                'description':screen_vals['body_text'] or "No Description",
                                'res_model':'poweremail.mailbox',
                                'res_id':mail_id
                                    }
                attid = att_obj.create(cr,uid,new_att_vals)
                if attid:
                    self.pool.get('poweremail.mailbox').write(cr,uid,mail_id,{'pem_attachments_ids':[[6, 0, [attid]]],'mail_type':'multipart/mixed'})