Unable to update WordPress plugin in Plesk: Cannot load the ionCube PHP Loader

Symptoms

1. Unable to update WordPress plugin:

   PLESK_ERROR: Failed loading /usr/local/ioncube/ioncube_loader_lin_5.2.so (http://ioncube_loader_lin_5.2.so/) : /usr/local/ioncube/ioncube_loader_lin_5.2.so (http://ioncube_loader_lin_5.2.so/) : undefined symbol: zend_block_interruptions Failed loading /opt/plesk/php/7.1/lib/php/modules/ioncube_loader_lin_7.0.so (http://ioncube_loader_lin_7.0.so/) : /opt/plesk/php/7.1/lib/php/modules/ioncube_loader_lin_7.0.so (http://ioncube_loader_lin_7.0.so/) : cannot open shared object file: No such file or directory 

   OR

   PLESK_ERROR: Installation "site": Cannot load the ionCube PHP Loader - it was already loaded Cannot load the ionCube PHP Loader - it was already loaded 

2. PHP version 7.1 is set up in Domains > example.com > Websites & Domains > PHP Settings. 
3. File /var/www/vhosts/system/example.com/etc/php.ini contains for following ionCube version:

   CONFIG_TEXT: zend_extension = /usr/local/ioncube/ioncube_loader_lin_5.2.so
   zend_extension = ioncube_loader_lin_7.0.so

Cause

Incorrectly specified path to ioncube_loader_lin_X.X.so. The path points to an incorrect version of ionCube (it is different from version of PHP set for the domain).

Resolution

Note: if you don't have root access to Plesk via SSH, contact your hosting provider regarding the issue

1. Connect to the server using SSH .
2. Open /var/www/vhosts/system/example.com/etc/php.ini of domain with such issue and comment out rows that point to incorrect versions of modules, for example:

   CONFIG_TEXT: ;;zend_extension = /usr/local/ioncube/ioncube_loader_lin_5.2.so
   ;;zend_extension = ioncube_loader_lin_7.0.so

3. Reread the PHP handler settings:

   # plesk bin php_handler --reread