Imported articles not found in some Queries

Hi there,

I’m using FeedWordPress to import Articles from a site into a custom post type “articles”. This works very nice, thanks for that!
Now I made a plugin, that gets new articles and sends them as mail.
The query for this:

$q = new WP_Query(array(
    'date_query' => array(
      'after' => $date,
    ),
    'post_type' => 'article',
    'nopaging' => true
  ));

When executing the cronjob manually it works and sends all articles, when I’m not triggering it, it only finds the manually inserted articles.
I have 3 different imported feeds and all of them are affected.
I tried query_posts() before which had the same result.
I also tried executing the cronjob serverside via crontab which didn’t change anything too.

Does anyone have an idea where I can continue digging about this – I am at my wit’s end.

Thanks in advance!