Hello @gavgeorge,
Our developers are currently checking your heavily modded Child theme. In the meantime, kindly temporarily deactivate these deprecated X - {Name} plugins.
Delete these plugins and install the latest ones that are available in our Themeco repository. You can go to X > Validation > Extensions.
If you can revert to the site backup, switch to the backup before any of these issues. Then, clone the working version in a staging area. You can do the updates and troubleshooting in the staging area. Once everything goes smoothly, that is the time to push all the updates to the live site. This is a MUST in doing updates to prevent disrupting the live when there are issues with the updates. Check out this documentation to set up a staging area: https://www.wpbeginner.com/wp-tutorials/how-to-create-staging-environment-for-a-wordpress-site/
Best Regards.
Kindly let us know how it goes.