NGiNX vs Apache: 500 error, how to solve?

Question

Nginx

Hey!
such a trouble - we set up a bunch of NGiNX vs Apache through the Plesk admin panel for a number of web sites on the host and for the time being everything worked fine, until the cache was cleared on one of them ( new-buildings.com ) and it started! .. The site lies issuing a message to the world Error displaying the error page: Call to a member function init() on null: String could not be parsed as XML gives the same message as on the main page.

Judging by the logs above, nginx gives the info normally, and the problem is on the part of apache.
We tried to edit .htaccess but so far without success, this is how it looks at the moment:

Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{QUERY_STRING} base64_encode[^(]*\([^)]*\) [OR]
RewriteCond %{QUERY_STRING} (<|%3C)([^s]*s)+cript.*(>|%3E) [NC,OR]
RewriteCond %{QUERY_STRING} GLOBALS(=|\[|\%[0-9A-Z]{0,2}) [OR]
RewriteCond %{QUERY_STRING} _REQUEST(=|\[|\%[0-9A-Z]{0,2})
RewriteRule .* index.php [F]
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteCond %{REQUEST_URI} !^/index\.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]

Corrected nginx.conf as suggested by Joomla developers https://docs.joomla.org/Nginx did not help either.. Tell me
, where could this ambush be??
Thanks