XML sitemap generated has invalid format if we check it against sitemap XSD.

To check it you can use this XML Validation tool. In demoauthor.magnolia-cms.com, create a sitemap for travel site and validate xml content (due to MGNLGS-119 url cannot be validated) against sitemap current XSD.

Result for each url:

Cvc-complex-type.2.4.a: Invalid Content Was Found Starting With Element 'changefreq'. One Of '{"http://www.sitemaps.org/schemas/sitemap/0.9":loc}' Is Expected.. Line '1', Column '78'.

This is believed to be resulting in a number of pages not being correctly indexed by Google. More information in ticket: SUPPORT-6137