You can try:
$output .= $modx->getChunk($tpl, array_merge($scriptProperties,[
'index-title' => $sectionOptions[0]['sectionTitle'],
'flexgrid-cols' => $sectionOptions[0]['sectionColumns'],
'limit' => $sectionOptions[0]['sectionLimit'],
'flexGrids' => implode("", $flexGrids),
]));
This should pass all scriptProperties