Theme LMS - Warning after Wordpress update 5.3.2

Hi everybody,
After the site is upgraded to Wordpress version 5.3.2, two warning lines appear on each page and the pages are no longer loaded.

Warning: preg_match() expects parameter 2 to be string, array given in /home/apima917/public_html/wp-includes/class-wp-block-parser.php on line 417

Warning: strlen() expects parameter 1 to be string, array given in /home/apima917/public_html/wp-includes/class-wp-block-parser.php on line 489

I deactivated and reactivated all the plugins (all ok) and I updated the theme to version 5.7, but it didn’t help.
By activating any of the Wordpress themes everything works, but obviously I lose the graphic functionality of the LMS theme and some pages are unusable.
I would also add that I have not made any customizations to the theme.
How can I solve it?

Thank you very much


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