Well if $value is the entire repeater you could do something like this:
// Set the first sock image uploaded as the featured image
function acf_set_featured_image( $value, $post_id, $field ){
if(isset($value) && is_array($value)){
delete_post_thumbnail( $post_id);
//Add the value which is the image ID to the _thumbnail_id meta data for the current post
add_post_meta($post_id, '_thumbnail_id', $value[0][sock_image]);
}
return $value;
}
// acf/update_value/name={$field_name} - filter for a specific field based on it's name
add_filter('acf/update_value/name=sock_images', 'acf_set_featured_image', 10, 3);
That is if you’ve set the return value of the image field to URL. Otherwise you’ll have to do a bit more with it..
But really you should activate wp_debug and do an error_log($value); inside the function to find out what value is first.
