Huge problem with the plugin

Hello I have a major problem. I have a news website and I use your plugin which fits perfectly. The problem is when is activated I cannot post a new article because it does now load the new post dashboard correctly. When I deactivate it everything works fine.

Error details
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one error type E_ERROR found in 361 line of the file
/home/bi342677/euosmos.gr/wp-content/plugins/directorist/includes/libs/vafpress/classes/metabox.php. Κωδικός σφάλματος: Uncaught Error: Call to a member function get_default() on null in /home/bi342677/euosmos.gr/wp-content/plugins/directorist/includes/libs/vafpress/classes/metabox.php:361
Stack trace:
#0 /home/bi342677/euosmos.gr/wp-content/plugins/directorist/includes/libs/vafpress/classes/metabox.php(181): VP_Metabox->_enfactor_field(Array, Object(VP_Metabox))
#1 /home/bi342677/euosmos.gr/wp-content/plugins/directorist/includes/libs/vafpress/classes/metabox.php(118): VP_Metabox->_enfactor(Array)
#2 /home/bi342677/euosmos.gr/wp-admin/includes/template.php(1310): VP_Metabox->_setup(Object(WP_Post), Array)
#3 /home/bi342677/euosmos.gr/wp-admin/edit-form-advanced.php(635): do_meta_boxes(Object(WP_Screen), ‘side’, Object(WP_Post))
#4 /home/bi342677/euosmos.gr/wp-admin/post-new.php(75): include(‘/home/bi342677/…’)
#5 {main}
thrown

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