After the Madrid upgrade, the Date/Time error validation is not as it was working in previous version (Only in portal). Ex: Catalog Item -Vulnerability Management Request Preferred time for scan is a Date/Time variable. On the portal the validation doesn't take place when you select the date on the calendar. You must click outside of the Calendar for the validation to take place, the field error to appear, and for the Calendar to go away.
This is a bug
The issue only occurs when the type of preferred_date variable is "Date/time".
As a workaround, you just need to set the variable type to "Date" only.