502 Bad Gateway - exit signal Segmentation fault

[macadan]

From few weeks ago we have a errors from our LAMP Plesk System in some CMS like wordpress:

/var/log/apache2/error.log
[notice] child pid 7358 exit signal Segmentation fault (11)

sudo tailf /var/log/nginx/error.log
[error] 7263#0: *5220 upstream prematurely closed connection while reading response header from upstream, client: 66.249.75.222, server: mundiario.com, request: "GET /galicia/feed/ HTTP/1.1", upstream: "http://198.27.69.41:7080/galicia/feed/", host: "mundiario.com"

apache2.conf:

<IfModule mpm_prefork_module>
StartServers 30
MinSpareServers 20
MaxSpareServers 100
ServerLimit 300
MaxClients 250
MaxRequestsPerChild 2000
</IfModule>

/etc/apache2/envvars:
APACHE_ULIMIT_MAX_FILES='ulimit -n 65536'
-------------------------------------------------------------

conf/last_nginx.conf:

proxy_pass https://198.27.69.41:7081;
proxy_connect_timeout 90;
proxy_send_timeout 90;
proxy_read_timeout 90;

proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
access_log /var/www/vhosts/mundiario.com/statistics/logs/webmail_access_ssl_log;

proxy_buffers 256 64k;
proxy_buffer_size 256k;
proxy_busy_buffers_size 256k;
proxy_temp_file_write_size 256k;
proxy_max_temp_file_size 0;

fastcgi_buffer_size 256k;
fastcgi_buffers 8 256k;


Any help will be welcome because we are completely stuck and without solution.