I use WP SEO by Yoast to generate sitemaps and the sitemap generated for custom types has a short hexa string at the beginning that invalidate the whole XML file :
148e2 <?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="//cabouge.tv5monde.com/main-sitemap.xsl"?> <urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:image="http://www.google.com/schemas/sitemap-image/1.1" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd" xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
You can see the live file here (problem solved on the live file).
The characters at the beginning of the files seams to be linked to the content, because they are different for another custom type.
I use WPSEO v18.104.22.168, but the bug was present with version 1.4.6. It seams to be linked to my server configuration, because I cannot reproduce it on a testing server with the same Wordpress code installed on it. The production server runs PHP 5.3.8.
I tried to disable all other plugins, but the issue is still present.
Any idea about where I could find the issue ?