The SEF-url for a static content item is generating (in debug) this link:

index.php?option=com_content&task=section&id=&Itemid=
instead of
index.php?option=com_content&task=view&id=58&Itemid=

With a static article titled "Fashion news" the SEF url is www.mydomain.com/Fashion_news/ this used to work fine, now it works fine with most articles except with new ones I create, in debug it now returns
index.php?option=com_content&task=section&id=&Itemid=

This used to work fine, but fails after upgrading to 5.7 (I'm using Joomla 1.0.15).
I emptied all the menu and content trash.
There are no sections or categories with the same name.