I upgraded our test site to 4.7.29 (type fixed) yesterday and the cron has been failing since then with a 500 server error.
We are running on Wordpress 4.9.2. The cron has been working successfully until now for years.
We have a cron job running every 30 minutes using the URL to cron.php method. I've checked the cron.php permissions; they haven't changed and have checked that the user and password are still valid and have enough permission (they do). When I run the command directly from the command line I also get a 500 internal server error, same with running it in a browser. The only thing we did was upgrade the version of CiviCRM. Help?