APO causing critical error in some geographic regions

Yesterday, Nov 30th, at around 11:00am MST, my StatusCake site monitoring tool began to report that my site was unreachable from multiple geographic locations. I confirmed this using additional, similar tools, and a VPN to try and get to it from those locations.

When trying to reach my site from these seemingly random locations, a regular visitor would be met with the “this wordpress site is experiencing a critical error” message. Normally I’d put that down to a plugin clash or theme issue, but since I could reach the site fine from many other locations, it had to be something geographically specific.

Digging into log files from my server I could see this error:

[error] 3450#3450: *3126876 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to undefined function get_current_screen() in /www/REMOVED FOR PRIVACY/public/wp-includes/script-loader.php:2465

The function get_current_screen is defined in wp-admin/includes/screen.php and I checked to make sure that this file still existed. It did. So my conclusion was that for some reason that file was randomly inaccessible from various geographic locations.

The only thing that came to mind was an APO issue, and sure enough when I turned APO off, the issue went away and my site has been “UP” ever since. Perhaps APO’s caching was failing to serve that one specific file for some reason from some specific locations? Never seen anything like that before.

Problem is, I just discovered that even though I pay for APO, I don’t have Cloudflare Pro, and that means I can’t get any support to tell anyone this.

Anyone ever seen something like this before? Obviously I have left APO disabled for now, but I like it and would love to turn it back on if this can be fixed.