Hey Padam,
Your case is some custom code in your injection plugin is conflicting with the latest version. As my colleague mentioned in the other thread, we cannot provide support for custom codes. It would be your responsibility to fix the custom code or make it compatible with the latest version of X and Cornerstone.
I’d just recommend that you set up a staging copy of your live site and do update X and Cornerstone in staging so you can see and fix the conflict in the custom code.
If the custom code problem is just CSS, maybe try moving the custom CSS codes in Theme Options > CSS.
Just note that we still could not guarantee that moving the CSS code would fix the issue.
If you want us to investigate custom code conflicts, you might want to consider signing up to our One or Elite service. In One, we answer questions beyond our products and in Elite, we do the customization for you.
Thanks.