Error public_html/wp-includes/kses.php

Hi,
I created 2 Custom Post Types (Jobs on Board and Training Courses)
Associated with these Post Types I created 3 Custom Taxonomies (On-board departments, for the Jobs on Board post Type; Regioni and Departments, for Corsi di Formazione). to make them I used the CPT UI plugin.
The posts are called to the page via an Elementor block taken from the Unlimited Elements plugin.
In order to organise the urls correctly and to ensure that the individual post's url has the Custom category, I used the Custom Post Type Permalinks plugin.
I am using Elementor Version 3.10.1.

If I now try to enter a post I get this error

Fatal error: Uncaught Error: Object of class WP_Error could not be converted to string in /home/customer/www/career.costacrociere.it/public_html/wp-includes/kses.php:1686 Stack trace: #0 /home/customer/www/career.costacrociere.it/public_html/wp-includes/kses.php(1686): preg_replace('/[\\x00-\\x08\\x0B...', '', Object(WP_Error)) #1 /home/customer/www/career.costacrociere.it/public_html/wp-includes/kses.php(718): wp_kses_no_null(Object(WP_Error), Array) #2 /home/customer/www/career.costacrociere.it/public_html/wp-includes/kses.php(2107): wp_kses(Object(WP_Error), 'post') #3 /home/customer/www/career.costacrociere.it/public_html/wp-content/plugins/elementor-pro/modules/dynamic-tags/tags/post-terms.php(108): wp_kses_post(Object(WP_Error)) #4 /home/customer/www/career.costacrociere.it/public_html/wp-content/plugins/elementor/core/dynamic-tags/tag.php(35): ElementorPro\Modules\DynamicTags\Tags\Post_Terms->render() #5 /home/customer/www/career.costacrociere.it/public_html/wp-content/plugins/elementor/core/dynamic-tags/manager.ph in /home/customer/www/career.costacrociere.it/public_html/wp-includes/kses.php on line 1686
There has been a critical error on this website.

What could have caused this error?

The site is not public and development takes place by modifying the Hots file