Hello @team-d,
Thanks for updating thread.
Most often 500 error is because of lack of available memory. I suggest you to increase memory limit by editing your wp-config.php file which can be located under the root of your WordPress installation and then try again.
Add the following lines into that file.
define( 'WP_MEMORY_LIMIT', '512M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
Another option is to upload Cornerstone files manually via FTP using programs like Filezilla. To upload latest version of Cornerstone file, please follow the instructions in following tutorial. Please scroll down to Manual Updates section.
To get started with Filezilla, FTP in the context of WordPress, please take a look at following tutorial:
Note: It’s a humble request not to add new replies after you have updated the thread as it pushes down the ticket back into the queue which increasing the response time.
Thanks.