Your company applies three different interest rates for customers based on their credit rating, which is classified as being Excellent, Fair, Poor or Unknown.
In the years past, clerks entered credit ratings manually, which resulted in some of them being mistyped.
To improve data entry accuracy you modify the Customers form so that the Credit_Rating item is a static list item that allows only those four values.
Users report to you that some of the customer records can no longer be accessed when they use the modified Customers form. How can you fix this problem?