HI @UFHH01
I have just moved from plesk 12.0 to 12.5 and getting same error which was not happening in plesk 12.0,
error Log: No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket /var/www/vhosts/system/mydomain.com/php-fpm.sock (*) failed
According to your last...