So, when you see everything die like that, it is a fatal error in PHP. This isn’t going to be anything that’s going to show up in your Google Chrome inspector as the issue is happening server-side, where you do not have errors setup to show. This issue would be a little easier to diagnose if you had PHP errors turned on in your PHP configuration. It’s generally pretty common that when you configure PHP, you have it setup to show such errors, just in general.
Honestly, I’d just contact your webhost and ask them to edit your php.ini or whatever to quickly switch PHP errors on, or explain to them what’s going on and they can check your server’s error logs for you. Having PHP errors on will help you to diagnose such issues in the future, as well. That is the most efficient way to know exactly what line of code in your WordPress install is causing the issue.
The problem, as you eluded to, happens just after
the_content function runs.
content-single.php is no longer used in the theme, so that wouldn’t be doing anything.
content.php is what’s used for displaying single posts. And
content-list.php is what’s used for displaying posts in a post list. So, if you truly haven’t edited
content-list.php, then most likely it’s nothing that you’ve done in any of the template parts because you said it happens with post lists.
Rather, I’d look at any kinds of filters you’ve put on WordPress’s “the_content” filter from your Child theme’s functions.php. Or possibly you’ve copied a function from the framework to your Child theme’s functions.php that the framework filters onto the_content, that has since been edited?