Hello,

seems like we managed to fix the iOS grid break problem. As you mentioned the problem was that the plugin was using bootstrap 3.

Posting the solution just in case someone faces the same problem.

Plugint that creates the problem : https://wordpress.org/plugins/wc-pickup-store/

Paste this snippet in the functions.php that removes bootstrap loaded from the plugin :

function custom_dequeue_styles() {
    wp_dequeue_style('wps_bootstrap');
}
add_action('wp_enqueue_scripts', 'custom_dequeue_styles', 99);

You can close this topic.
Thanks!