I posted what you mentioned above. Meanwhile, I got this answer as a possible thing to check out:
Are you using the debug flag enabled in your wp-config.php?
If yes, can you try disable it, changing:
define( ‘WP_DEBUG’, true );
define( ‘WP_DEBUG’, false);
Do you think that can be the issue? I tried to find wp-config.php and I only found functions.php in the Appearance > Editor.
How can I check the wp_debug if it is true or false?