Production of additional evidence: Tribunal may permit documents or witnesses for sufficient cause or call evidence suo motu. Rule 23 bars parties from producing additional oral or documentary evidence before the Tribunal except that the Tribunal may, for reasons recorded and for sufficient cause or where opportunity has been lacking, allow documents, witnesses or affidavits to be produced or examined. Such evidence may be taken before the Tribunal or before a departmental authority directed by the Tribunal, which must comply and transmit records to the Tribunal. The Tribunal may also suo motu call for documents or summon witnesses to meet the ends of justice.