Formula field from Multi picklist not updating

Question

I have two custom objects "Customer Use Case" and "Use Case" where "Use Case' is a Lookup on the "Customer Use Case" - I have created a formula field (ROI__c)on the Customer Use Case object which looks at the related Use Case - The (ROI_Use_c) field on the Use Case field is multi-select.

The formula field is populated properly if the value in Use Case is the first one, but if it is any other, or multiple selections, it just returns the first value. If I change the value in the (ROI_Use_c) field on the Use Case and go back to the Customer Use Case the new value is not displayed?

Here is the Formula:

IF(INCLUDES( Use_Case__r.ROI__c , "Board of Directors"), "Board of Directors" + BR() , NULL) + IF(INCLUDES( Use_Case__r.ROI__c , "C-Level "), "C-Level " + BR() , NULL) + IF(INCLUDES( Use_Case__r.ROI__c , "Compliance "), "Compliance " + BR() , NULL) + IF(INCLUDES( Use_Case__r.ROI__c , "Human Resources "), "Human Resources " + BR() , NULL) + IF(INCLUDES( Use_Case__r.ROI__c , "Incident Management "), "Incident Management " + BR() , NULL) + IF(INCLUDES( Use_Case__r.ROI__c , "Security "), "Security ", NULL)

Answer 1

Remove all NULL instances and replace with empty string ("") - I think this will work, because when you add a string to NULL it generally returns NULL

Example:

IF(INCLUDES( Use_Case__r.ROI__c , "Board of Directors"), "Board of Directors" + BR() , "") + 
IF(INCLUDES( Use_Case__r.ROI__c , "C-Level "), "C-Level " + BR() , "") + 
IF(INCLUDES( ....