ESAPI (Extended Security API) creates error messages that are pointing towards missing user access rights for Objects/Fields:
You don't have the required permission (Create Access on X). If necessary, contact the administrator. Type: FIELD_ACCESS_VIOLATION Reason: NO_READ Object: Event Field: pt__PortatourActivity__c
Users confronted with this error should be assigned the permission sets portatour® User static and portatour® User dynamic!