Plugin prevents an unrelated function working

Hi there, love the plugin but it does have an odd effect on some code I regularly use in my functions.php file. The following code allows a child page to automatically change its page template to match that of its parent, upon saving:

//Change Page template to Parent type
add_action('save_post','changeTemplateOnSave');
if ( ! function_exists( 'changeTemplateOnSave' ) ) {
    function changeTemplateOnSave() {
        global $post;
        if ($post) {
            $curr_tmp = get_post_meta( $post->ID, '_wp_page_template', true );
            if ( $post->post_parent ) {
                $parent_tmp = get_post_meta( $post->post_parent, '_wp_page_template', true );
                update_post_meta( $post->ID, '_wp_page_template', $parent_tmp, $curr_tmp );
            }
        }
    }
}

For some reason, the above code only works if I deactivate the Strong Testimonials plugin! Do you know if there is a fix?