I used this code for sort my flexible content. Basic is the same code for repeater.
<?php
$acontecimentos = get_field('acontecimentos');
$date = [];
//Reorder
foreach($acontecimentos as $key => $row) {
$date[$key] = $row['data'];
}
array_multisort($date, SORT_ASC, $acontecimentos);
foreach($acontecimentos as $row) {
if($row['acf_fc_layout'] == 'galeria'):
//code
endif;
}
?>
After array_multisort you can use shuffle http://us3.php.net/manual/en/function.shuffle.php
