The bug has been fixed. There is a problem on your Wordpress blog, some sort of caching plugin is serving an outdated version of your RSS feed.
We found a solution to bypass the cache by adding a random parameter to the URL query string. Now the most recent posts have been imported.
For more information on our investigation, please see this ticket:
https://forum.fivefilters.org/t/missing-posts-in-feed/1561