Here are a few other suggestions to try.
(Unfortunately, I am unable to replicate the problem that you are currently experiencing so I cannot try the following suggestions myself to know whether or not theyu will help in your scenario.)
(1) Try changing line 148 of the 'wp-juicebox/config.php' file to the following:
echo $new_dom_doc->saveXML($new_settings_tag);(2) Try adding the following on line 147 of the 'wp-juicebox/config.php' file:
ob_clean();(3) Try removing line 3 of the 'wp-juicebox/config.php' file:
header('Content-type: application/xml');If any of the above work, please post back to let me know.
Thank you.