Check and make sure the properties exist and or the when rules being referenced exist. Also, check that there are no typos in the rules being referenced. I would try saving with only the first validation and see if that saves fine. If not trouble shoot that line first and than the second. This will help to narrow down with validation is causing the issue.
The error you are showing - '** Invalid expression or reference: No suitable instance found
@(Pega-ProcessEngine:WorkUtilities).pxIsAttachmentOfCategoryInCase(ClipboardProperty,String,String)' is because the function is looking for an Attachment and what you have selected in your screenshot is a PageList property 'EmploymentEligibilityDocumentAttachments'. Select the EmploymentEligibilityDocument under Process - Attachment Category without the "." .