And I received this email after I updated the plugin:
Since WordPress 5.2 there is a built-in feature that detects when a plugin or theme causes a fatal error on your site, and notifies you with this automated email.
In this case, WordPress caught an error with one of your plugins, Cornerstone.
Error Details
An error of type E_ERROR was caused in line 22 of the file /www/wp-content/plugins/cornerstone/includes/elements/definitions/button.php. Error message: Uncaught Error: Call to undefined function x_values_element_button() in /www/wp-content/plugins/cornerstone/includes/elements/definitions/button.php:22
Stack trace:
#0 /www/wp-content/plugins/cornerstone/includes/classes/elements/class-element-manager.php(106): require_once()
#1 /www/wp-content/plugins/cornerstone/includes/classes/elements/class-element-manager.php(98): Cornerstone_Element_Manager->load_files(Array, ‘/www/wp-content…’)
#2 /www/wp-content/plugins/cornerstone/includes/classes/elements/class-element-manager.php(9): Cornerstone_Element_Manager->register_native_elements()
#3 /www/wp-content/plugins/cornerstone/includes/utility/plugin-base.php(248): Cornerstone_Element_Manager->setup()
#4 /www/wp-content/plugins/cornerstone/includes/utility/plugin-base.php(290): Cornerstone_Plugin_Base->loadComponent(‘Element_Manager’)
#5 /www/wp-content/plugins/cornerstone/includes/classes/elements/class-element-front-end.php(28): Cornerstone_Plugin_Base->component(‘Element_Manager’)
#6 /www/wp-includes/class-wp