Since the update to joomla 3.9.0 I get an error on my website when I publish the related articles extension.
In some categories there is no problem, articles just show normally. But in some other categories articles won't show anymore, I get an empty page with only this message:
Warning: require_once(/home/testactief.nl/public_html/libraries/joomla/filesystem/folder.php): failed to open stream: No such file or directory in /home/testactief.nl/public_html/plugins/content/relatednews/core/helper_base.php on line 11

Fatal error: require_once(): Failed opening required '/home/testactief.nl/public_html/libraries/joomla/filesystem/folder.php' (include_path='.:/usr/share/php') in /home/testactief.nl/public_html/plugins/content/relatednews/core/helper_base.php on line 11

When I disable the plugin, all categories work fine again.

Do you know what is the problem?

Hello There!
I have the same problem. Please let me know on how to solve this.
Thanks a lot!

Regards,
Meavin