This bug will be fixed in Visforms 3.12.4
The bug is easy to fix, because only 3 lines of code in one file are involved.
Open the file administrator\components\com_visforms\models\visdatas.php
Replace the code at line 408 - 410
$where = ' and c.includefieldonexport = 1';
$where .= (!(empty($params->exppublishfieldsonly))) ? ' and c.published = 1' : '';
$where .= " and c.typefield NOT in('submit', 'image', 'reset', 'fieldsep', 'pagebreak')";
with
$where = ' includefieldonexport = 1';
$where .= (!(empty($params->exppublishfieldsonly))) ? ' and published = 1' : '';
$where .= " and typefield NOT in('submit', 'image', 'reset', 'fieldsep', 'pagebreak')";