Hi @alexander
Using Beta4 and I created a Condition on an item today and it threw the page I did it on into a Critical Error state - all other pages and parts of the site are fine.
The condition was set on a 4 cell Grid here as a test
Here is the error I got sent.
Error Details
An error of type E_ERROR was caused in line 372 of the file /public_html/wp-content/themes/pro/cornerstone/includes/_classes/class-condition-rules.php. Error message: Uncaught ArgumentCountError: Too few arguments to function Cornerstone_Condition_Rules::expression_string_is(), 1 passed and exactly 2 expected in /public_html/wp-content/themes/pro/cornerstone/includes/_classes/class-condition-rules.php:372
Going back to 5.1.5 resolved the error.
Thanks, Tom.