@siamajor
Thank you for reporting the problem! If this error occurs again, try to catch the text of the error and let me know.
@krassavchik
Hi,
1. What version of Php do you use?
2. What is your version of WordPress?
3. What are your installed plugins?
I think this is a php error. Try to turn on php errors and take a screenshot that you will see on your screen after the activation of the new version.
There is a good instruction on how to enable php errors:
https://digwp.com/2009/07/monitor-php-errors-wordpress/
Best regards, Alex