Using a combination of business rules of type "change value to" and "is invalid/is required" leads to a member incorrectly being marked as "Invalid" or "Valid".
Using a business rule to change the value of a required DBA will incorrectly succeed, even if the value set by the business rule is an incorrect code for the linked entity. In this case, the "Is Required" business rule succeeds, and the member is reported as Valid.
According to my analysis, the "Is Required" business will check if ANY value is assigned to the attribute, and not if a valid/existing code is assigned. In other words, the business rule will evaluate the "Is Required" prior to to the resolution of the value into an existing member. The result is that the required attribute is blank, but the Is Required rule succeeds.