Call to a member function getNode() on string in meta-box-template.php

Hi,

Each time we edit a post in WordPress, we get an error message as below. We’ve edited the error message in order to not show the exact path of our website, but the message it’s the same. The warnings messages that normally come out when posting a note are also not shown.

What could be the issue? Thanks.

PHP Fatal error: Uncaught Error: Call to a member function getNode() on string in /var/www/example.com/wp-content/plugins/fb-instant-articles/meta-box/meta-box-template.php:97\nStack trace:\n#0 /var/www/example.com/wp-content/plugins/fb-instant-articles/meta-box/class-instant-articles-meta-box.php(114): include()\n#1 /var/www/example.com/wp-includes/class-wp-hook.php(286): Instant_Articles_Meta_Box::render_meta_box('')\n#2 /var/www/example.com/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters('', Array)\n#3 /var/www/example.com/wp-includes/plugin.php(453): WP_Hook->do_action(Array)\n#4 /var/www/example.com/wp-admin/admin-ajax.php(100): do_action('wp_ajax_instant...')\n#5 {main}\n thrown in /var/www/example.com/wp-content/plugins/fb-instant-articles/meta-box/meta-box-template.php on line 97, referer: https://example.com/wp-admin/post.php?post=123456&action=edit&tab=0