Plone sitemap rejected by google

Google rejects my sitemap as being invalid.
This is confirmed by other sitemap tools. for example finds an incorrect http header content-type.
My Plone installation is nearly fresh, no further customizations.

It's about the sitemap.xml.gz provided by Plone in @@site-controlpanel.

Is this a known bug? Does anyone experience the same problem?
What can I do that google likes my sitemap?

Tested with Plone 5.08

More details please..what are the specific errors? What is your site URL.

A fresh Plone site passes without issues.

Well, it seems a "problem in chair, not in computer"

This needs further investigation...:confused: