Blog items won't load anymore after update

Yes it points in that direction.
But I can't seem to figger out what the problem is.
Any Idea where I should look?

What do you have in the child theme functions.php ?
I would begin by temporarily removing the code from there.
Then add any function back one by one to see which is the issue.

Hi,

I emptied the function.php file and it didn't change anything.
In the meanwhile I've checked my other templates I've have added code to.
In the footer.php I found a slight change where you add a hook.

<?php
/**
 * generate_after_footer hook.
 *
 * @since 2.1
 */
do_action( 'generate_after_footer' );

wp_footer();
?>

This is new once I added it. everything worked fine again.

Aah ok - so its working now ?

Yes somehow that hook broke the theme.
updated all my templates to be sure and futureproof

Glad to hear that!