Could you try this replacement for sources/news_sitemap.php:
https://raw.githubusercontent.com/ocproducts/composr/f5f67d0298c48a96df6636b1f4ee8951db39a7c5/sources/news_sitemap.php
It will fix a problem with shared-install support and also replace the directory if somehow it's gone missing.
To be more specific, if I set the "validate news" at "off" I don't get this message.
Then if after creating the news, I validate it, I don't get this error
But if I try to create a news and leave the "Validate" at "On" then I get the error
Could you try this replacement for sources/news_sitemap.php:
https://raw.githubusercontent.com/ocproducts/composr/f5f67d0298c48a96df6636b1f4ee8951db39a7c5/sources/news_sitemap.php
It will fix a problem with shared-install support and also replace the directory if somehow it's gone missing.