Been using ACF for around 6 months and never even knew this. What an amazing feature I’ve totally been missing!
Cheers John, forget that then, I’ve just removed the action.
For anyone interested, or has had the same issue, I solved this myself. Value to become values and the singular value to loop through each array item:
<?php
$field = get_field_object('choices');
$values = $field['value'];
foreach ($values as value) :
$rows = get_field('gallery_repeater', 'option');
$specific_row = $rows[$value];
$sub_field_value = $specific_row['gallery'];
?>
<?php foreach ($sub_field_value as $img) : ?>
<div data-src="<?php echo esc_url($img['sizes']['large']); ?>" title="<?php echo esc_attr($img['title']); ?>">
<img />" alt="<?php echo esc_attr($img['alt']); ?>" title="<?php echo esc_attr($img['title']); ?>" />
</div>
<?php endforeach ?> // $img
</div>
<?php endforeach ?> // $value