It would be best to setup a staging site and do the update from there so that the live site will not be affected in case there will be any issues with the update and you will be able to do some testing.
Here are some search results on how to setup a staging site:
In case you are not certain how to proceed, you might want to check with your web host and ask them if they can help you with the staging site.
Here is a link for a details information on how to do an update:
Please remember to clear all caches when updating so that the code from the latest release is always in use. This will help you to avoid any potential errors or any unexpected display issue on the site.
Kindly also make sure that if you update X, you will also need to update Cornerstone to avoid compatibility issues.
In case you are still seeing an issue, please provide us with the admin access to your site in a Secure Note (key icon under the replies you post/posted):
Hope this helps.