yii2 ExportMenu results empty page if columns > 10 - yii2

Question

I'm using kartik\export\ExportMenu to provide csv exports.
If I want to export approx. more that 10 columns it results just a empty page with no error. Also the yii error log has no entry. With less columns it works.
I tried the following settings but none of them solved it:
'batchSize' => .. tried from 100 to 1000
'streamAfterSave' => false
In case of streaming after file creation it creates any empty file (0B).
Any ideas? Thanks.
--- snip ---
<?php
$fullExportMenu = ExportMenu::widget([
'dataProvider' => $dataProvider,
'columns' => $gridColumns,
'emptyText' => 'Keine Daten verfügbar.',
'fontAwesome' => true,
'filename' => 'Webshop_Produkte',
'showColumnSelector' => false,
//'noExportColumns' => [0,1]
//'pjaxContainerId' => 'kv-pjax-container',
'dropdownOptions' => [
'label' => 'Alle Daten',
'class' => 'btn btn-default'
],
'batchSize' => 500,
//'target' => ExportMenu::TARGET_POPUP,
'stream' => false,
'streamAfterSave' => false,
'afterSaveView' => '#app/views/webshop-product/download',
'folder' => '#app/web/downloads',
//'linkPath' => '/downloads',
//'exportConfig' => $exportConfig,
]);
echo $fullExportMenu . ' ' .
GridView::widget([
'dataProvider' => $dataProvider,
'filterModel' => $searchModel,
'columns' => $gridColumns,
'pjax' => true,
'pjaxSettings' => ['options' => ['id' => 'kv-pjax-container']],
'panel' => [
'type' => GridView::TYPE_PRIMARY,
'heading' => '<h3 class="panel-title"><i class="glyphicon glyphicon-book"></i> Datei Export</h3>',
],
// set a label for default menu
'export' => [
'label' => 'Aktuelle Seite',
'fontAwesome' => true,
],
// your toolbar can include the additional full export menu
'toolbar' => [
'{export}',
// $fullExportMenu,
['content' =>
Html::a('<i class="glyphicon glyphicon-repeat"></i>', ['index'], [
'data-pjax' => 0,
'class' => 'btn btn-default',
'title' => Yii::t('kvgrid', 'Reset Grid')
])
. ' ' .
Html::submitButton('Tabelle leeren', ['name' => 'truncate', 'class' => 'btn btn-danger',
'data-confirm' => 'Wollen Sie wirklich die Tabelle leeren?'
. 'Achtung: Löschen kann nicht rückgänig gemacht werden.'
])
. ' ' .
Html::submitButton('Alles', ['name' => 'download', 'class' => 'btn btn-danger',
'data-confirm' => 'Wollen Sie wirklich alles exportieren?'
])
],
]
]);
?>
--- snap ---