[Plugin: WordPress SEO – Sitemap] following pages are empty

Good morning from germany,

I have some trouble with the WordPress SEO sitemap-feature.

The index page (https://amrum-news.de/sitemap_index.xml) is loading correctly, as well as the post-sitemap1.xml, page-sitemap.xml and author-sitemap.xml.

Problem is the post-sitemap2.xml, 3.xml etc. only show a blank page and give me an error in the google webmaster tools. If I check the source of those there is content into it, but its not displayed for whatever reason.

If I change the amounts of listings within one sitemap page from 1k to 5k for example, the plugins deletes sitemap 2 and 3 since its enough space in sitemap 1, but then the same problem appears to this one – if I change it back to 1k sitemap 1 works again, 2 & 3 are being creating and still won’t work.

I don’t get an error at the plugin page and really don’t know what the problem could be.
I’d be very glad is someone could help me out here ??

Thanks
B.