Catch Everest Free Theme – Google Analytics code won't save in header

Hello, I'm using the Catch Everest Free theme on a WordPress multisite. After the most recent update, I can no longer add the Google Analytics tracking code to the theme header (from the WP backend) without it breaking the theme and having to revert to the previous version of the theme. Instead of updating normally as it has for the last couple of years, I get an error message saying something about having to add it via PHP. Why is this, and is there a way around this (without installing any plugins)? Thanks!