Displaying image from a group field

Hi,

I'm new to this kind of thing, and having some problems. Hope I'm posting in the right place.

I'm trying to put together a way to display book data by series for an author website. So I have created the SERIES post type which has custom fields for information about the series, and then a cloneable group book_data to add the data for each book in that series. I'm using an Oxygen repeater (using the Oxygen 3.9 beta for Meta Box integration).

However, I can't work out how to get the cover image to display as anything other than a thumbnail. This wasn't an issue for the series cover image, which is not in the cloneable group.

I've tried using a code block instead, and that way I can get non-thumbnail images, but they all appear in each instance of the repeater, so each book shows as having every cover in the series. Here's the code I used:

<?php
$my_group = rwmb_meta( 'book_data' );
foreach ( $my_group as $group_value ) {
    $images = isset( $group_value['book_image_advanced_u1tymdel9bn'] ) ? $group_value['book_image_advanced_u1tymdel9bn'] : array();
    foreach ( $images as $image ) {
        $image = RWMB_Image_Field::file_info( $image, array( 'size' => 'medium' ) );
        // print_r( $image );
        echo "<img src='{$image['url']}' />";
    }
    ?>
        <?php
}
?>